EnvoyACP/XF Application Programming Manual Abstract This manual is intended for application programmers who use EnvoyACP/XF to communicate with remote computers and terminals. Product Version EnvoyACP/XF F40 Supported Releases This manual supports G02.00 and all subsequent G-series releases until otherwise indicated a new edition. Part Number Published Release ID 132179 May 1997 G02.
Document History Part Number Product Version Published 132179 EnvoyACP/XF F40 May 1997 New editions incorporate any updates issued since the previous edition. Ordering Information For manual ordering information: domestic U.S. customers, call 1-800-243-6886; international customers, contact your local sales representative. Document Disclaimer Information contained in a manual is subject to change without notice.
Contents About This Manual ix Notation Conventions xiii 1.
2. Asynchronous Balanced Mode (ABM) Protocols (continued) Contents 2.
3. Normal Response Mode (NRM) Protocols (continued) Contents 3.
Contents B. Features Common to Bit-Synchronous Protocols B.
Figures (continued) Contents Figures (continued) Figure 3-4. Figure 3-5. Figure 3-6. Figure 3-7. Figure 3-8. Figure 3-9. Figure B-1. Figure B-2. Figure B-3. Figure B-4.
Contents EnvoyACP/XF Application Programming Manual– 132179 viii
About This Manual About This Manual This manual describes how application processes on a Himalaya S-series server can use EnvoyACP/XF to perform bit-synchronous communications. Along with the EnvoyACP/XF Configuration Manual, this manual replaces the EnvoyACP/XF Reference Manual.
EnvoyACP/XF Manuals About This Manual Section or Appendix Title Contents A File-System Errors Summarizes the file-system errors that may be returned by EnvoyACP/XF. B Features Common to Bit-Synchronous Protocols Describes synchronous data transmission, the message-framing format, data-code transparency, multiple-frame transmission before acknowledgment, and error detection through cyclic redundancy checking. Glossary Defines the terms used in this manual. EnvoyACP/XF Manuals Figure i.
Related Manuals and Standards About This Manual Related Manuals and Standards You also should have access to the technical manuals and standards documents listed below.
Your Comments Invited About This Manual EnvoyACP/XF Application Programming Manual– 132179 xii
Notation Conventions General Syntax Notation The following list summarizes the notation conventions for syntax presentation in this manual. UPPERCASE LETTERS. Uppercase letters indicate keywords and reserved words; enter these items exactly as shown. Items not enclosed in brackets are required. For example: MAXATTACH lowercase italic letters. Lowercase italic letters indicate variable items that you supply. Items not enclosed in brackets are required. For example: file-name [ ] Brackets.
General Syntax Notation Notation Conventions An ellipsis immediately following a single syntax item indicates that you can repeat that syntax item any number of times. For example: "s-char..." Punctuation. Parentheses, commas, semicolons, and other symbols not previously described must be entered as shown. For example: error := NEXTFILENAME ( file-name ) ; LISTOPENS SU $process-name.
Notation for Messages Notation Conventions !o:i. In procedure calls, the !o:i notation follows an output buffer parameter that has a corresponding input parameter specifying the maximum length of the output buffer in bytes. For example: error := FILE_GETINFO_ ( filenum , [ filename:maxlen ] ) ; !i !o:i Notation for Messages The following list summarizes the notation conventions for the presentation of displayed messages in this manual. Nonitalic text.
Notation for Messages Notation Conventions % Percent Sign. A percent sign precedes a number that is not in decimal notation. The %þnotation precedes an octal number. The %Bþnotation precedes a binary number. The %Hþnotation precedes a hexadecimal number.
1 EnvoyACP/XF and the Application Task This section describes the relationship between EnvoyACP/XF and your application program.
File-System Procedures EnvoyACP/XF and the Application Task Figure 1-1.
EnvoyACP/XF and the Application Task Definition of Station READ[X] SETMODE[NOWAIT] WRITE[X] WRITEREAD[X} For further information on how you can use these file-system procedures with EnvoyACP/XF, see Section 4, System Procedure Call Specifics for EnvoyACP/XF. Definition of Station The ADCCP protocol standard defines “station” as a method of data link control.
EnvoyACP/XF and the Application Task Application Tasks Application Tasks When communicating with stations over a bit-synchronous communications line, an application process must perform certain line-handling tasks.
EnvoyACP/XF and the Application Task Multiple FILE_OPEN_ Calls If you need to issue more than 15 READ or WRITE calls, you can issue multiple FILE_OPEN_ calls. EnvoyACP/XF supports multiple FILE_OPEN_ calls for all protocols. Note. When more than one user opens a line, all users must synchronize the request to the EnvoyACP/XF process. If you want to prevent another user from accessing a line, use the exclusion mode within FILE_OPEN_.
EnvoyACP/XF and the Application Task Multiple Pending Nowait Operations Note that, except for SETMODE 30, you issue only one of the necessary SETMODE and CONTROL calls for each line, regardless of how many FILE_OPEN_ calls you issue. You can issue the SETMODE and CONTROL calls to any one of the multiple line openings. It makes no difference which opening you use.
EnvoyACP/XF and the Application Task Setting Line-Configuration Parameters Setting Line-Configuration Parameters Line-configuration parameters specify the following characteristics: • • • • • • • • • • • • • Type of line (full-duplex or half-duplex) Type of local station (primary, secondary, or combined) Type of connection (switched or nonswitched) Type of electrical interface (RS-232 or RS-422) Polling interval (for NRM) T1 timer (for ABM) Window size Maximum frame size Size of control field Size of ad
EnvoyACP/XF and the Application Task Establishing and Controlling a Data Link Establishing and Controlling a Data Link Your application establishes a link and performs line-control operations through calls to the CONTROL procedure. These calls include numerical operation codes, several of which vary from one protocol to another. Note. If the IOP fails, EnvoyACP/XF automatically puts the link back in logical disconnect state (LDS).
EnvoyACP/XF and the Application Task Line Ready Considerations Line Ready Considerations The following text describes various Line Ready considerations. Nonswitched Lines Always issue a CONTROL 11 or CONTROL 17 to ensure that DTR is enabled. If DSR remains false because of a problem with a modem, cabling, or other hardware, a request that causes a READ or WRITE to the line completes but returns file-system error 140 (modem error).
Transferring Data EnvoyACP/XF and the Application Task Establishing a Connection The procedure calls for establishing a connection depend upon whether the line is switched or nonswitched: Switched Nonswitched FILE_OPEN_ (no connection) FILE_OPEN_ (now have connection) SETMODE (optional)* SETMODE (optional)* 1. CONTROL 17,0 SETMODE 16 (until have connection) or 2. CONTROL 17, 1 or CONTROL 11 (now have connection) CONTROL 11 and 17 optional * Note that SETMODE 16, 17, or 19 reinitializes the link.
EnvoyACP/XF and the Application Task WRITE, READ, and WRITEREAD Requests and Nowait I/O the next instruction or statement. An AWAITIO procedure call later in the program logically completes such a call. The EnvoyACP/XF bit-synchronous protocols queue all nowait READ, WRITE, and WRITEREAD requests. Using basic control fields, your application can have up to 7 WRITE requests and 7 READ requests queued at any one time.
EnvoyACP/XF and the Application Task Shutting Down a Data Link operate efficiently when you use Two-way Simultaneous transmission (TWS). (See Two-Way Alternate (TWA) Versus Two-Way Simultaneous (TWS) Operation on page 310 for more information about using TWA and TWS.) Shutting Down a Data Link An application normally shuts down the data link by using the CONTROL 18 procedure to send a DISC command.
Automatic Calling for V.25 bis Modems EnvoyACP/XF and the Application Task Automatic Calling for V.25 bis Modems This section describes how EnvoyACP/XF supports automatic calling for V.25 bis modems. If you do not require this function, you may skip this section. V.25 bis is a CCITT protocol recommendation for serial modems that have automatic calling capability. The hardware configuration and the software environment for V.25 bis support is illustrated in Figure 1-2. Figure 1-2. EnvoyACP/XF for V.
Your Application and V.25 bis EnvoyACP/XF and the Application Task The contents of V.25 bis communications are made up of ASCII strings that handle the call-establishment (such as providing the number to be dialed) and call-clearing (such as handling call failure) functions. Some V.25 bis commands specify dialing calls to a preprogrammed or stored telephone number. The modem determines the scope of V.25 bis commands (issued from the DTE) and indications (responses from the modem).
Your Application and V.25 bis EnvoyACP/XF and the Application Task Call Establishment To establish a call for an automatic calling procedure, your application must direct the EnvoyACP/XF (DTE) to perform these three functions. Function Procedure 1. Ensure that the modem (DCE) is available for operation. CONTROL 17, parameter 1 2. Provide the telephone number. WRITE a UI frame by setting bits 3 through 7 of the MCW to zero, and sending CRNnnnnnnn in the information block. 3.
Your Application and V.25 bis EnvoyACP/XF and the Application Task modem; an auto-answer modem is sufficient. However, a V.25 bis modem allows the receiving side to answer selectively or to reject incoming calls. Table 1-2 summarizes the modem requirements. Table 1-2. Modem Requirements Station Modem Optional/Required Calling station V.25 bis-compatible Required Receiving station V.
Your Application and V.25 bis EnvoyACP/XF and the Application Task Table 1-4 shows the procedure calls required to establish a call when the primary station uses a V.25 bis modem and the secondary station uses a regular auto-answer modem. Table 1-4. Establishing a Call With Only One V.25 bis Modem Calling Station (with V.25 bis modem) Receiving Station (with regular auto-answer modem) FILE_OPEN_ line. FILE_OPEN_ line. SETMODE 16—set line characteristics. SETMODE 16—set the line characteristics.
Your Application and V.25 bis EnvoyACP/XF and the Application Task ! Enable DTR--Get ready to interact with the modem. CONTROL fnum, 17, 1 if error then error_process; ! This should not occur ! An error returned at this time indicates that the modem is ! not in V.25 bis mode. A parameter value of "1" indicates ! that the DTE must wait for the indication from the modem.
Your Application and V.25 bis EnvoyACP/XF and the Application Task Figure 1-4. Outgoing Call V.25 bis DTE ServerNet WAN Concentrator DCE V.25 bis Modem CRNnnnn (dialing the number) either INV and CFI (invalid command and call failure) or VAL and CFI (valid command but call cannot be connected)* *Termination sequences are vendor dependent 050 Figure 1-5 shows how the V.25 bis commands and indications are used during an incoming call. Figure 1-5. Incoming Call V.
EnvoyACP/XF and the Application Task Your Application and V.25 bis Call Collisions Outgoing and incoming calls may collide, but only on rare occasions. The following considerations may affect how you decide to handle collisions: • • • Since the incoming call is unknown information, you may wish to give priority to the incoming call. You can transmit the outgoing call afterwards.
Your Application and V.25 bis EnvoyACP/XF and the Application Task Figure 1-6 shows the interface circuits for V.25 bis. Figure 1-6. Interface Circuits for V.25 bis DTE ServerNet WAN Concentrator DCE V.25 bis Modem Raises DTR on circuit 108 (indicating DTE READY) Holds DSR low on circuit 107 (indicating V.
EnvoyACP/XF and the Application Task Your Application and V.
2 Asynchronous Balanced Mode (ABM) Protocols This section describes application considerations for the Asynchronous Balanced Mode (ABM) protocols supported by EnvoyACP/XF. The protocols described here are HighLevel Data Link Control (HDLC) and Advanced Data Communications Control Procedures Asynchronous Balanced Mode (ADCCP-ABM). ABM Features EnvoyACP/XF allows you to use HDLC or ADCCP-ABM to establish an ABM data link between two combined stations. You can use ABM only for point-to-point configurations.
ABM Link-Level Commands Asynchronous Balanced Mode (ABM) Protocols Figure 2-1 shows station addressing for combined stations. The two stations each maintain a link-level send (Ns) and receive (Nr) sequence number to ensure the proper sequencing of information frames. Figure 2-1.
Asynchronous Balanced Mode (ABM) Protocols ABM Link-Level Responses ABM Link-Level Responses EnvoyACP/XF automatically transmits the following link-level responses from the local station to the remote station (these responses are transparent to the application program): RR Receive Ready (I-frame acknowledgment; ready to accept more data) RNR Receive Not Ready (I-frame acknowledgment; no more I-frames can be accepted) REJ Reject (I-frame acknowledgment; out-of-sequence I-frame received) SREJ Selecti
ABM Application Process Interface Asynchronous Balanced Mode (ABM) Protocols Figure 2-2.
Asynchronous Balanced Mode (ABM) Protocols Opening a Line summarizes the EnvoyACP/XF error codes. This section specifies any considerations particular to ABM. Opening a Line The communications line must be opened before any transmissions can take place. The application does so by calling the OPEN procedure. Be aware of the following restrictions on the OPEN procedure: • • • Multiple OPEN calls require that access be shared. If a line is opened for exclusive access, the line can be opened only once.
Extended Address Field Asynchronous Balanced Mode (ABM) Protocols should ensure that the station addresses for the local and remote computer systems are configured compatibly. Extended Address Field You can use SCF to change the ADDRESSSIZE modifier to enable the extended address format or you can use the SETMODE 116 procedure call. If the address size is no more than 2-octets, you can use SETMODE 16 to specify the primary/combined station and secondary/combined station.
Timers and Number of Retries Asynchronous Balanced Mode (ABM) Protocols Timers and Number of Retries When transmission errors occur, EnvoyACP/XF always retries the requested operation. HDLC and ADCCP-ABM use timeouts to detect errors. EnvoyACP/XF supports these timeouts as follows: Features Default Value Modifier SETMODE procedure Timeout 5 seconds T1TIMER SETMODE 15 Determines the period that EnvoyACP/XF waits for an acknowledgment from the remote station after sending any frame.
Timers and Number of Retries Asynchronous Balanced Mode (ABM) Protocols Figure 2-3. T1TIMER and RR Frame Retry Count Retry Count = 3 RR Frame Retry Count WRITE Operation Issued Send I-Frame 0 (No Response; Timeout) Send RR,P 1 (No Response; Timeout) 2 Send RR,P (No Response; Timeout) Send RR,P 3 (No Response; Timeout) WRITE Operation Aborted with File-System Error Code 162. 013 In the ABM protocol, the primary and the secondary station use the T1TIMER similarly.
Reject (REJ) Asynchronous Balanced Mode (ABM) Protocols Figure 2-4.
Asynchronous Balanced Mode (ABM) Protocols Selective Reject (SREJ) You enable or disable the REJ command/response by setting bit 7 of parameter 1 in a SETMODE 16 call, as follows: CALL SETMODE (fnum,16,parameter1,parameter2) parameter1.<7> = 0: disable REJ command/response = 1: enable REJ command/response You enable or disable the SREJ command/response by setting bit 0 of parameter 2 in a SETMODE 116 call, as follows: CALL SETMODE (fnum,116,parameter1,parameter2) parameter2.
Asynchronous Balanced Mode (ABM) Protocols Transferring Data within a Tandem system issues a CONTROL (fnum,18,1) call to switch the system from disconnected to offline. Transferring Data Once a link has been established, your application can begin transferring data. Transmitting I-Frames To transmit an I-frame, the application program places the data to be sent in a buffer and calls the WRITE procedure.
Shutting Down a Data Link Asynchronous Balanced Mode (ABM) Protocols The parameter value specifies the state that the local station goes into upon the receipt of a UA or DM response from the remote station or upon timeout. The disconnect state is indicated by the parameter, as follows: 0 = disconnected 1 = offline Figure 2-5.
Pseudocode Examples Asynchronous Balanced Mode (ABM) Protocols Pseudocode Examples These examples show the recommended logic for basic data-communication tasks. These are not actual code examples. Initiating and Terminating an HDLC Link The following example shows the configuration, initiation, and termination of an HDLC link. The stations are connected to one another over a nonswitched, full-duplex line. In this example, the line is called $HDLC.
Asynchronous Balanced Mode (ABM) Protocols Initiating and Terminating an ADCCP-ABM Link Initiating and Terminating an ADCCP-ABM Link The following example shows the initiation of an ADCCP-ABM link. The stations are connected over a nonswitched, full-duplex line. This example specifies the following variables: • • • • • Multiple opens (3) Nowait I/O for each OPEN Open depth of 15 Extended control Nowait operations complete in any order The line is called $ADCP.
Asynchronous Balanced Mode (ABM) Protocols Initiating and Terminating an ADCCP-ABM Link When either application wants to terminate the session, the application calls CONTROL 18 and closes the line. A single CONTROL call is enough, but the application must issue a CLOSE for each OPEN procedure, as follows: !Disconnect the line CONTROL fnum^1,18) AWAITIO fnum^1 !Close the line; conversation is complete.
Asynchronous Balanced Mode (ABM) Protocols Initiating and Terminating an ADCCP-ABM Link EnvoyACP/XF Application Programming Manual– 132179 2- 16
3 Normal Response Mode (NRM) Protocols This section describes application considerations for the Normal Response Mode (NRM) protocols supported by EnvoyACP/XF. The protocols described here are Synchronous Data Link Control (SDLC) and Advanced Data Communications Control Procedures Normal Response Mode (ADCCP-NRM). NRM Features EnvoyACP/XF allows you to use SDLC or ADCCP-NRM to establish an NRM data link for point-to-point or multipoint configurations.
Normal Response Mode (NRM) Protocols NRM Application Process Interface NRM Application Process Interface The application process controlling an EnvoyACP/XF SDLC or ADCCP-NRM station interacts with the data link through: • • • Calls to Guardian file-system procedures Condition codes (CCE, CCG, and CCL) returned by the procedures and numerical error codes returned by the FILEINFO procedure Application-level data transferred through I-frames and U-frames This section describes considerations particular to
Normal Response Mode (NRM) Protocols Primary or Secondary Station Although you can set these characteristics during system configuration and can modify them later by using SCF, you should also use the SETMODE procedure to ensure that the line characteristics always meet the requirements of the application process. For additional information on the SETMODE procedure, see SETMODE Procedure on page 4-13 A brief description of the line characteristics listed above follows.
Extended Control Fields Normal Response Mode (NRM) Protocols 2: 3: 3-octet address field 4-octet address field The address-field size that you select when you call SETMODE 19 applies only for the duration of the current line opening. For multipoint supervisor application processes, you must issue the SETMODE 19 call before building the station address list. Extended Control Fields By using the SETMODE and CONTROL procedures, you can configure either a 1-octet or a 2-octet control field.
Normal Response Mode (NRM) Protocols Polling Interval contain a two-byte control field; unnumbered frames contain the basic one-byte control field. So, for IBM extended control, only the following numbered frames contain a two-byte control field: • • • • • Information frames (I-frames) Receive Ready frames (RR-frames) Receive Not Ready frames (RNR-frames) Reject frames (REJ-frames) Selective Reject frames (SREJ-frames) The default setting specifies that the IBM extended control format is not enabled.
Timers and Number of Retries Normal Response Mode (NRM) Protocols EnvoyACP/XF waits the amount of time specified in the poll interval for the next WRITE request. If the poll interval expires before another WRITE request is received, EnvoyACP/XF transmits an RR frame with the poll bit set. EnvoyACP/XF allows you to select either a 1-octet or 2-octet control field.
Timers and Number of Retries Normal Response Mode (NRM) Protocols Table 3-1. Timers and Number of Retries (continued) Features Retry count Default Value Modifier SETMODE procedure .5 seconds IDLETIME R SETMODE 16 For a primary or supervisor station, T1TIMER determines the interval between polling cycles. 3 retries L1RETRY SETMODE 15 Determines the retry count for level-1 error recovery attempts such as WRITE operation failures and DSR failures.
Timers and Number of Retries Normal Response Mode (NRM) Protocols Figure 3-1. T1TIMER and RR Frame Retry Count Retry Count = 3 WRITE Operation Issued RR Frame Retry Count Send I-Frame,P 0 (No Response; Timeout) Send RR,P 1 (No Response; Timeout) 2 Send RR,P (No Response; Timeout) Send RR,P 3 (No Response; Timeout) WRITE Operation Aborted with File-System Error Code 162.
Timers and Number of Retries Normal Response Mode (NRM) Protocols Figure 3-2.
Normal Response Mode (NRM) Protocols Two-Way Alternate (TWA) Versus Two-Way Simultaneous (TWS) Operation Two-Way Alternate (TWA) Versus Two-Way Simultaneous (TWS) Operation Two-way alternate (TWA) operation allows frames to be sent in only one direction over the line at any given time. Two-way simultaneous (TWS) operation allows frames to be sent in both directions at the same time. Operation Line Type Frames can be sent...
Normal Response Mode (NRM) Protocols ASCII/EBCDIC Line Code For a multipoint supervisor station, the tributary to which frames are being sent is independent of the tributary from which frames are being received. That is, as long as the supervisor station has WRITE requests pending, the supervisor can transmit data to any tributary, regardless of whether the supervisor is receiving frames from a specific tributary. Only one station can own the P/F bit at any one time.
Normal Response Mode (NRM) Protocols Reject (REJ) Reject (REJ) The REJ command or response indicates that the specified I-frame was received in error and requests retransmission of the indicated I-frame and all subsequent I-frames. For modulo-8 frame sequencing, this type of error recovery causes EnvoyACP/XF to retransmit at most seven frames. For modulo-128 frame sequencing, however, the REJ command or response can introduce substantial inefficiency.
Normal Response Mode (NRM) Protocols Establishing and Controlling a Data Link Mode, the primary-station application issues a CONTROL 14 call. In a primary station, this call sends a Set Initialization Mode (SIM) command frame to the secondary stations. In a supervisory station, the CONTROL 14 function uses the auto-poll capability of EnvoyACP/XF to send a SIM frame to all tributaries.
Link Establishment with IBM SDLC Loop Controller Normal Response Mode (NRM) Protocols Figure 3-3. Standard NRM Link Establishment Tandem NonStop System Primary/Supervisor Station Tributary Stations ServerNet WAN Concentrator SNRM DM SNRM DM Primary station places the nonresponding station(s) in an error-stop state.
Link Establishment with IBM SDLC Loop Controller Normal Response Mode (NRM) Protocols Figure 3-4.
Normal Response Mode (NRM) Protocols Transferring Frames Your application uses the DEFINELIST procedure call to pass the station list to EnvoyACP/XF. EnvoyACP/XF refers to the specified addresses of multipoint tributary stations by using a station index in the second byte of the Message Control Word (MCW) in the READ or WRITE buffer. The station index refers to the order in which the DEFINELIST procedure call defines the station addresses. A supervisor application uses a READ call to initiate polling.
Normal Response Mode (NRM) Protocols Message Control Word (MCW) Message Control Word (MCW) Your application must place an MCW into the first two bytes of its buffer: Point-to-point environment Generally, set the MCW to 0. However, you can use the first byte of the MCW to specify some of the less-frequently used U-frame command/responses (UI, UP, XID, TEST, and NonReserved). Always set the second byte to 0 for point-to-point configurations.
Normal Response Mode (NRM) Protocols NRM Basic Message Transmission reserve WRITEREAD requests for special functions, such as sending U-frames (that is, U-frames for which you must specify the MCW rather than issuing a CONTROL call). Do not use WRITEREAD requests routinely for sending I-frames. SETMODE 30 allows nowait I/O operations to complete on the application level in the order of their completion by the I/O process, rather than in the order in which they were issued.
Normal Response Mode (NRM) Protocols Multipoint Polling Multipoint Polling When a multipoint supervisor application is not sending receiving frames, it can cause EnvoyACP/XF to poll all tributary stations specified in the DEFINELIST station list to determine whether any tributary has data to transmit. The auto-poll feature of EnvoyACP/XF systematically transmits a poll frame (RR,P) to each tributary station in the DEFINELIST station list and checks for a response.
Normal Response Mode (NRM) Protocols Responses to a Poll If the response is an RR or RNR frame and if the response contains the proper station identification in the address field, polling continues at the next entry. (For more information about the RR and RNR frames, see S-Frame Command/Response Codes on page B-7.
Nonresponding Station List Normal Response Mode (NRM) Protocols Nonresponding Station List EnvoyACP/XF maintains a nonresponding station list to track the stations that do not respond to polling. If a polled station does not respond with data or a supervisory frame within the configured timeout period, EnvoyACP/XF puts the station address on the nonresponding station list. EnvoyACP/XF considers stations on the list to be in an error-stop state and does not poll them during subsequent polling cycles.
Station List Format Normal Response Mode (NRM) Protocols addr^d = %42000, entry^size = 4, num^entries = 4, polling^count = 4, ! Station D address ! Entry size (4 octets) ! Number of entries in list ! Number of polling addresses ! in station list array polling^type = 0, ! Continuous polling no^poll = 1; ! Disable poll state bit ! The station address is one octet left-justified; ! addr^a = A, null INT .
Station List Format Normal Response Mode (NRM) Protocols CALL DEFINELIST (fnum,station^list,entry^size,num^entries, polling^count,polling^type); The following example applies to ADCCP-NRM only (extended address mode).
Sending Mode-Setting Commands Normal Response Mode (NRM) Protocols [ addr^ab15,2 * [0], addr^ab25,2 * [0], addr^ab35,2 * [0] ]; ! Station AB15 entry ! Station AB25 entry ! Station AB35 entry CALL DEFINELIST (fnum,station^list,entry^size,num^entries, polling^count,polling^type); ANSI ADCCP Basic for Extended Address Format When two Tandem computer systems communicate by using the extended addressing capability of EnvoyACP/XF ADCCP, the bit combinations of the address field octets are not restricted.
Normal Response Mode (NRM) Protocols • • Sending Mode-Setting Commands One specific tributary station Only disabled tributary stations Sending to All of the Tributaries When sending to all stations, EnvoyACP/XF makes one complete pass through the defined station list. If all tributaries respond properly (UA), the operation completes with CCE. If one tributary responds improperly or not at all, EnvoyACP/XF retries polling that station up to the configured number of times.
Shutting Down a Data Link Normal Response Mode (NRM) Protocols Sending to Stations in an Error-Stop State You can issue the mode-setting function only to those stations that have encountered a response timeout failure (that is, stations in an error-stop state) by using a parameter value of 4. This feature permits you to perform periodic retries of failed stations. Shutting Down a Data Link When stations operate in NRM, only the primary station can shut down the link.
Normal Response Mode (NRM) Protocols • Shutting Down a Data Link To transmit DISC to all the tributaries on the defined station list: CALL CONTROL 18(fnum) CONTROL 18 disconnects all responding stations. Nonresponding stations are placed on the nonresponding list. You must issue READ procedures and check the returned MCW to determine which stations are not responding. • To transmit DISC to a subset of tributaries in the defined station list: 1.
Shutting Down a Data Link Normal Response Mode (NRM) Protocols Figure 3-6. Secondary Station Issues CONTROL 18,0 Primary Station Secondary Station User Issues CONTROL 18 or CONTROL 18,0 Station goes into Logical Disconnect State (LDS). RR, P DM 046 Note. If a primary station sends a SNRM to a secondary station, the secondary station responds with a UA unless an error occurs or the secondary station is in disconnected mode.
Normal Response Mode (NRM) Protocols SDLC and ADCCP-NRM Error Handling SDLC and ADCCP-NRM Error Handling EnvoyACP/XF returns two general types of errors: line errors and link errors. Line errors These are errors such as garbled transmission. EnvoyACP/XF retransmits the I-frame up to the retry threshold before informing the application.
Normal Response Mode (NRM) Protocols NRM READ Procedure The effect of a READ request depends on the type of station your application is controlling and on whether any received frames are present in the input buffer: Type of Station Effect of a READ Request Multipoint supervisor When no received frames or WRITE requests are queued, READ initiates the polling process. Subsequent READ requests are queued and completed as the multipoint supervisor receives frames from the remote stations.
NRM READ Procedure Normal Response Mode (NRM) Protocols Figure 3-8. Standard I-Frame Acknowledgment Supervisor Station Tributary Stations (NR/NS) 01 RR–P 1 (0) 01 I–F (0, 0) 01 RR (1) 02 RR–P (0) 02 RR–F (0) 01 RR–P (1) 2 3 4 5 6 Legend 1 The supervisor station polls tributary station 01 by sending it an RR–frame with the poll bit set. 2 Tributary station 01 responds by sending back an I–frame with the final bit set.
NRM WRITE Procedure Normal Response Mode (NRM) Protocols The example in Figure 3-9 assumes the presence of two tributary stations (address 01 and address 02) and shows the OPTION1 method of I-frame acknowledgment. Figure 3-9. Delaying I-Frame Acknowledgment Supervisor Station Tributary Stations (NR/NS) 01 RR–P 1 01 I–F (0) (0, 0) 02 RR–P (0) 02 RR–F (0) 01 RR–P (1) 2 3 4 5 Legend 1 The supervisor station polls tributary station 01 by sending it an RR–frame with the poll bit set.
Normal Response Mode (NRM) Protocols NRM WRITEREAD Procedure WRITE operation completion depends on the type of frame being sent: Sending I-frames The WRITE operation completes at the link level when the remote station acknowledges the receipt of the frame. Sending command/ response U-frames The WRITE operation completes at the link level as soon as EnvoyACP/XF sends the frame.
Pseudocode Examples Normal Response Mode (NRM) Protocols Pseudocode Examples The examples in this subsection show the basic logic behind initializing a NRM link. These are not actual code examples. SDLC Point-to-Point Primary Station This example shows how to initiate an SDLC link for a point-to-point primary station that performs two-way alternate communication over half-duplex, nonswitched line facilities. In this example, the line name is $SDLC0.
Normal Response Mode (NRM) Protocols ADCCP-NRM Point-to-Point Primary Extended This SETMODE call ensures that the system-generation parameters are set as follows: • • • • • Point-to-point primary station Full-duplex line facilities (two-way simultaneous operation) Nonswitched lines REJ supervisory frame allowed RS-232C line interface For switched line facilities, include the connection requests after the SETMODE call, but before the first READ.
Normal Response Mode (NRM) Protocols SDLC Point-to-Point Secondary SETMODE fnum^1,19,,%30000 If <> do error handling !Send SNRME CONTROL fnum^1,13,3 If <> do error handling AWAITIO fnum^1 If <> do error handling . . . Setting Line Configuration Parameters For both SDLC and ADCCP-NRM, you also can include additional SETMODE calls for operations 15, 17, 18, 19, and 30 to ensure that all line-configuration parameters are set.
Normal Response Mode (NRM) Protocols ADCCP-NRM Point-to-Point Secondary !Bits 3 through 7 of the MCW should contain the value %20 and !the AWAITIO call should complete with CCG (indicating that !the received frame generated a nonzero MCW) AWAITIO fnum If <> do error handling ADCCP-NRM Point-to-Point Secondary The example below shows how to open and initialize an ADCCP point-to-point secondary-station application that performs two-way, alternate communication over halfduplex, nonswitched, line facilities.
Normal Response Mode (NRM) Protocols SDLC Multipoint Supervisor !the AWAITIO call should complete with CCG (indicating that !the received frame generated a nonzero MCW) AWAITIO fnum If <> do error handling For the READ operation, there are two points at which a condition code is returned: • • When the actual call is issued. When the associated operation is completed by the AWAITIO call. When the call is issued, a CCG or CCL indicates that the call was unacceptable to either Guardian or to EnvoyACP/XF.
Normal Response Mode (NRM) Protocols ADCCP-NRM Multipoint Supervisor !Multipoint supervisor station !Half-duplex line facilities (two-way alternate operation) !Nonswitched lines !Accept all addresses !RS-232C line interface !Use of 1-second poll interval (100 * 10 milliseconds) SETMODE fnum,16,%1002,100 If <> do error handling !Define station list !This DEFINELIST call passes a station list to EnvoyACP/XF, !specifying the station addresses of all tributary stations !that the multipoint supervisor is contr
Normal Response Mode (NRM) Protocols SDLC Multipoint Tributary !RS-232C line interface !Use of 1-second poll interval (100 * 10 milliseconds) SETMODE fnum^1,16,%1002,100 If <> do error handling !The following SETMODE call specifies !2-octet address field !2-octet control field SETMODE fnum^1,19,,%30000 If <> do error handling !Define station list !This DEFINELIST call passes a station list to EnvoyACP/XF, !specifying the station addresses of all tributary stations !that the multipoint supervisor is contro
Normal Response Mode (NRM) Protocols SDLC Multipoint Tributary !accept all addresses !RS-232 line interface SETMODE fnum,16,%1003 If <> do error handling !Define addresses to which tributary will respond DEFINELIST fnum,poll^list,addr^size,num^entries,poll^count,0 If <> do error handling !The following READ call enables the read unit of !EnvoyACP/XF in preparation for receiving the !SNRM command from the supervisor station.
ADCCP-NRM Multipoint Tributary Normal Response Mode (NRM) Protocols ADCCP-NRM Multipoint Tributary The example below is for an ADCCP multipoint tributary station application that performs two-way alternate communication over half-duplex, nonswitched, line facilities. In this example, the line name is $TRIB2. The application uses a 2-octet address field, a 2-octet control field, and three line openings.
Normal Response Mode (NRM) Protocols NRM Nonswitched Point-to-Point The configured device name of the primary-station line is $PRIM; the configured device name of the secondary-station line is $SEC. After opening their respective lines, each application process calls the SETMODE procedure to ensure that the required line characteristics are properly defined, as follows: PRIMARY INT lnr [0:11] := ["$PRIM ", 9 * [" "]], pnum; SECONDARY INT lnr [0:11] := ["$SEC", 10 * [" "]], snum; . .
NRM Nonswitched Point-to-Point Normal Response Mode (NRM) Protocols command or response. The applications must examine bits 3 through 7 of the MCW in the read buffer to determine which command or response was received. For example, a SNRM code in MCW.<3:7> is %20. The link is now in NRM. In the primary station, upon posting a READ, EnvoyACP/XF begins polling the secondary station by sending Receive Ready (RR) frames with the P bit set.
NRM Nonswitched Point-to-Point Normal Response Mode (NRM) Protocols The first WRITE call terminates polling. Each WRITE call sends an I-frame. EnvoyACP/XF controls setting the P-bit because the stations are configured for fullduplex operation: PRIMARY I-Nr(0),Ns(0) ———————————> I-Nr(0),P,Ns(1) ———————————> SECONDARY READ loop accepts incoming frames. For each AWAITIO completion, check for CCL (error), CCE (more frames to come), and CCG (last frame. EnvoyACP/XF acknowledges the two received frames.
SDLC and ADCCP-NRM Nonswitched Multipoint Operation Normal Response Mode (NRM) Protocols SDLC and ADCCP-NRM Nonswitched Multipoint Operation The example below shows how to use file-system procedures and error returns in an EnvoyACP/XF, centralized, multipoint configuration using two-way, alternate, communication over half-duplex, nonswitched, line facilities. For simplicity, only the activities of the supervisor process and one tributary process are given.
Normal Response Mode (NRM) Protocols addr^b,3 * [0], addr^c,3 * [0], addr^d,3 * [0] ]; SDLC and ADCCP-NRM Nonswitched Multipoint Operation ! Station B ! Station C ! Station D CALL DEFINELIST (pnum,station^list,entry^size,num^entries,poll^count, poll^type); The tributary also uses DEFINELIST to pass a station list to EnvoyACP/XF. However, in this case, the station list contains only those addresses to which the tributary application process itself responds.
Normal Response Mode (NRM) Protocols SUPERVISOR CALL CONTROL(pnum,13,0); IF <> THEN CALL ERROR^PROC; CALL AWAITIO (pnum); IF <> THEN CALL ERROR^PROC; SDLC and ADCCP-NRM Nonswitched Multipoint Operation TRIBUTARY CALL READ(snum, read^buf1,2); IF <> THEN CALL ERROR^PROC; CALL READ (snum, read^buf2,2);r); IF <> THEN CALL ERROR^PROC; CALL AWAITIO (snum); IF <= THEN CALL ERROR^PROC; CALL AWAITIO (snum); IF <= THEN CALL ERROR^PROC; For each station address in the tributary process, the AWAITIO associated with
Normal Response Mode (NRM) Protocols SDLC and ADCCP-NRM Nonswitched Multipoint Operation <————————— A,I-Nr(0),Ns(1),F line turnaround ——————> [A,RR,Nr(2),P] ———————> <————————— line turnaround <————————— [A,RR,F] line turnaround ——————> [B,RR,P] —————————————> <————————— line turnaround <————————— [B,RR,F] line turnaround ——————> B,I-Nr(0),Ns(0) ——————> B,I-Nr(0),Ns(1) ——————> B,I-Nr(0),Ns(2) ——————> B,I-Nr(0),Ns(3) ——————> B,I-Nr(0),Ns(4),P ————> <————————— line turnaround <————————— [B,RR,Nr(5),F] [C,RR
Normal Response Mode (NRM) Protocols SDLC and ADCCP-NRM Nonswitched Multipoint Operation EnvoyACP/XF Application Programming Manual– 132179 3- 50
4 System Procedure Call Specifics for EnvoyACP/XF This section describes EnvoyACP/XF-specific information for Guardian file-system procedures. For complete information see the Guardian Procedure Calls Reference Manual. Table 4-1 lists the file procedures that your application can use to interact with EnvoyACP/XF, bit-synchronous, data-communication lines. . Table 4-1. File-system Procedures Used With EnvoyACP/XF AWAITIO[X] Completes a previously initiated I/O operation on an EnvoyACP/XF line.
System Procedure Call Specifics for EnvoyACP/XF CONTROL Procedure Table 4-1. File-system Procedures Used With EnvoyACP/XF (continued) SETMODE [NOWAIT] Defines one or more line characteristics. SETMODENOWAIT Performs identically to SETMODE except that it is performed as a nowait operation. WRITE[X] Transmits data from the buffer to the remote station by way of a single I-frame or transmits the unnumbered command or response specified by bits 3 through 7 of the MCW.
System Procedure Call Specifics for EnvoyACP/XF CONTROL Procedure input tag INT(32):value applies to nowait I/O only. tag is a value you define to identify uniquely the operation associated with this CONTROL call. Condition Codes = (CCE) indicates that the CONTROL procedure was executed successfully. < (CCL) indicates that an error occurred (call FILE_GETINFO_). Example CALL CONTROL (fnum,19); fnum is the one-word integer variable returned by the OPEN call that opened the communications line.
System Procedure Call Specifics for EnvoyACP/XF CONTROL Procedure Table 4-2. CONTROL Function Codes (page 2 of 3) Function Code Parameter Description parameter-1 .<0> = 0: Sends a SIM command to all stations. = 1: Sends a SIM command to a specific station, as indicated in .<8;15> (only NRM multipoint). = 1: Sends a RSET command (ABM). .<1:15> = 4: Sends a SIM only to those stations that were in an error-stop state. .
System Procedure Call Specifics for EnvoyACP/XF CONTROL Procedure Table 4-2. CONTROL Function Codes (page 3 of 3) Function Code 19 Parameter Description .<0> = 1, .<8:15> = station index value: Specifies the station that is to receive the DISC command. NRM Trib .<0> = 0, NRM Trib .<15> = 0: Switches the local station to the Logical Disconnected state (LDS), so that the station responds with DM to all messages from the primary station (other than SNRM). NRM Trib .<0> = 0, NRM Trib .
System Procedure Call Specifics for EnvoyACP/XF DEFINELIST Procedure DEFINELIST Procedure Use the DEFINELIST procedure when the application process acts as a supervisor or tributary station in a centralized, multipoint configuration. EnvoyACP/XF requires that you build a list of station addresses within the supervisor application and each tributary application. A single tributary application controlling one physical line can respond to more than one station address.
System Procedure Call Specifics for EnvoyACP/XF Station List Format input station-list INT:ref is the name of an integer array that you supply; station-list contains one or more station addresses. input entry-size INT:value is the name of an integer variable that you supply; the variable specifies the size, in words, of an entry in the station-list array. Note that the entry size varies somewhat from one protocol to another.
Station List Format System Procedure Call Specifics for EnvoyACP/XF the station addresses to which that station responds. In both cases, you use the DEFINELIST procedure to pass the station list to EnvoyACP/XF. Each entry in the station list is referenced by a station index in the range 0 through 255. The first entry in the list is entry 0, the second is entry 1, and so forth.
Priority Polling System Procedure Call Specifics for EnvoyACP/XF CALL DEFINELIST (fnum,station^list,entry^size,num^entries, poll^count,poll^type); In the following example, another tributary application responds to a single station address: LITERAL addr^c = %41400, entry^size = 4, num^entries = 1, poll^count = 1, poll^type = 0; ! ! ! ! ! station C address entry size (4 words) number of entries in list number of entries in list dummy parameter INT .
READ[X] Procedure System Procedure Call Specifics for EnvoyACP/XF addr^ab35,2 * [0] ]; ! Station AB35 entry CALL DEFINELIST (fnum,station^list,entry^size,num^entries, polling^count,polling^type); Note. Even though EnvoyACP/XF allows you to specify an extended address field for all protocols, be aware that the SDLC protocol standard does not support the extended address field. See the IBM Synchronous Data Link Control General Information Manual.
System Procedure Call Specifics for EnvoyACP/XF READ[X] Procedure input read-count (Use with both READ and READX) INT:value specifies how many incoming bytes can be placed in the application buffer. You must supply this value to EnvoyACP/XF. Note that this value must include the two bytes used for the MCW. output count-read INT:ref:1 INT .
READ[X] Procedure System Procedure Call Specifics for EnvoyACP/XF Bits 3-7 = Value specifies a command/response code for a U-frame. This value causes EnvoyACP/XF to place the appropriate command/response code into bits 0, 1, 2, 4, and 5 of the control field of the U-frame. See Table 4-3. Bits 8-15 = For point-to-point applications, the content of bits 8 through 15 is zero.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure Condition Codes = (CCE) indicates that the READ[X] procedure was executed successfully. = (CCL) indicates that an error occurred (call FILE_GETINFO_). Examples In the following example, fnum is the number returned by the OPEN call that opened the communications line, and in^buffer is the name of the integer array within the application program into which EnvoyACP/XF places the received data.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure The form of the SETMODE procedure is: CALL SETMODE ( filenum filenum , function , parameter-1 , parameter-2 ,[ last-params ] ); !i !i !i !i !o input INT:value is the number returned by the OPEN call that opened the line. In a SETMODE call, you supply this variable to EnvoyACP/XF. function input INT:value is an integer value you use to specify the desired SETMODE function to EnvoyACP/XF. Table 4-4 lists the SETMODE codes.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure In Table 4-4, the system-configuration modifiers analogous to the particular SETMODE commands are included in parentheses. Asterisks indicate the SETMODE function codes that reset the link. Table 4-4. SETMODE Function Codes (page 1 of 4) Function Code Parameter 15 Description Set retry parameters. paramete r-1 Retry timer. Timeout duration, in 10-centisecond (.01) units. (See T1TIMER modifier) The default timer is 5 seconds.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure Table 4-4. SETMODE Function Codes (page 2 of 4) Function Code Parameter Description .<13> 0: Secondary station (See SECONDARY modifier) 1: Primary station (See PRIMARY modifier) .<14:15> 0: Point-to-point (Use for NRM only) 2: Multipoint supervisor (Use for NRM only) 3: Multipoint tributary (Use for NRM only) paramete r-2 For NRM lines, specifies polling interval (See IDLETIMER modifier) in 10-centisecond units.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure Table 4-4. SETMODE Function Codes (page 3 of 4) Function Code Parameter 18 * Description Set statistics threshold, flag fill, and window size. paramete r-1 The threshold value. When the sum of CRC errors, command reject errors, and retries exceeds this threshold, appropriate statistics are displayed at the operator console. This parameter is picked up as an 8-bit field.
System Procedure Call Specifics for EnvoyACP/XF SETMODE Procedure Table 4-4. SETMODE Function Codes (page 4 of 4) Function Code Parameter Description .<1:2> 0: 1-octet address field 1: 2-octet address field 2: 3-octet address field 3: 4-octet address field (See ADDRESSSIZE modifier) .<3> 0: 1-octet control field 1: 2-octet control field (See EXTENDEDCONTROL modifier) .
System Procedure Call Specifics for EnvoyACP/XF WRITE[X] Procedure fnum is the one-word integer variable specified in the open call that opened the communications line, and %1003 is an octal value that sets parameter-1.
System Procedure Call Specifics for EnvoyACP/XF WRITE[X] Procedure input write-count INT:value specifies how many bytes are to be retrieved from the application buffer. You supply the value to EnvoyACP/XF. Note that this value must include the two bytes used for MCW. If the WRITE[X] call is transmitting an unnumbered command or response, the buffer need contain only the MCW and write-count should be 2. count-written INT:ref:1 INT .
WRITE[X] Procedure System Procedure Call Specifics for EnvoyACP/XF For WRITE[X] or WRITEREAD[X] requests, the format of the MCW is: Bit 0 Bit 1 Bit 2 = 0: Do NOT set P/F bit. = 1: Set P/F bit. = 0: The frame is a numbered I-frame. Return completion when the remote station acknowledges a successful receipt. = 1: The frame is a command/response U-frame. Return a completion immediately. = 0: The information field is present in this command/response Uframe. Note.
WRITE[X] Procedure System Procedure Call Specifics for EnvoyACP/XF Table 4-5. MCW Values for U-Frame Command/Response Codes (page 2 of 2) MCW.<3:7> Decimal Value MCW.<3:7> Octal Value U-Frame Command U-Frame Response 26 %32 nonreserved 3 nonreserved 3 28 %34 TEST TEST 31 %37 BCN (an IBM command) Examples In the following example, the write-count of 102 specifies that an I-frame containing 100 bytes of data is to be transmitted (remember that this count also includes the 2-byte MCW).
A File-System Errors This appendix summarizes the EnvoyACP/XF file-system errors. If your local operating procedures require contacting the Tandem NonStop Support Center (TNSC), supply your system number and the numbers and versions of all related products as well. Table A-1 lists the errors in numerical order.
File-System Errors Table A-1. Summary of Errors (page 2 of 4) FileSystem Error Relevant Protocol Description Recovery 12 all File in use. Check your program and recode if necessary. Possible causes are misspelling in the code, wrong line specified, or multiple lines opened for exclusive access. This error could also be an operation error. 21 all Illegal read count or write count specification. Supply proper count with the READ, WRITE, or WRITEREAD request.
File-System Errors Table A-1. Summary of Errors (page 3 of 4) FileSystem Error Relevant Protocol 160 Description Recovery all Request invalid for line state: • Requested WRITE, WRITEREAD, or Control 14 (send RSET) operation when the line was disconnected or offline. • Requested WRITE or WRITEREAD would have caused more WRITE operations to be concurrently pending than maximum specified when the line was opened.
File-System Errors Table A-1. Summary of Errors (page 4 of 4) FileSystem Error Relevant Protocol 170 171 172 Description Recovery NRM WRITE request for multipoint line had invalid station entry number, or station entry number different from currently active output entry number. Supply valid number in MCW. NRM Primary No response to poll, command, or WRITE. Retry or perform higher-level recovery; the specific action is device dependent. NRM Secondary Not being polled. Place station in LDS.
Error Recovery and Fault-Tolerant Operation File-System Errors 30-33 System configuration problem 120-199 Device hardware problem 200-255 Path error, hardware malfunction, or network error Error Recovery and Fault-Tolerant Operation EnvoyACP/XF uses file-system error codes to inform the application program that the CPU executing the EnvoyACP/XF communications process failed or that an SCF command switched control of the line to another CPU.
File-System Errors Error Recovery and Fault-Tolerant Operation EnvoyACP/XF Application Programming Manual– 132179 A- 6
B Feat s Protocols Bit-synchronous protocols provide the following features: • • • • • Synchronous data transmission Message-framing format, in which specific bit patterns delineate message blocks Data-code transparency Multiple-frame transmission before acknowledgment, which reduces the requisite number of line turnarounds Error detection for addressing, control, and data integrity through cyclic redundancy checking Message Formats In a bit-synchronous communications environment, messages are divided
Address Field Features Common to Bit-Synchronous Protocols Zero-Bit Insertion (Bit-Stuffing) Your application must make provisions for zero-bit insertion or deletion. Zero-bit insertion removes the risk that a sequence of six consecutive 1 bits (which could be confused for a flag) might occur randomly within the other fields of the frame. EnvoyACP/XF automatically inserts a zero bit immediately, after any sequence of five consecutive one bits (Figure B-2).
Control Field Features Common to Bit-Synchronous Protocols • • Identifies the sequence number of sending frames (when sending data) Acknowledges frames received The primary or combined station uses the control field to instruct the addressed secondary or combined station to perform a specific operation. The secondary or combined station also uses the control field to respond to the remote primary or combined station. Note.
Control Field Features Common to Bit-Synchronous Protocols Frame Format Types There are three frame formats, specified by the control code (the least-significant bits) of the control field: Frame Format Control Code Type Bit 0 Bit 1 Information (I-frame) 0 x Supervisory (S-frame) 1 0 Unnumbered command-response (U-frame) 1 1 All control fields contain some combination of the following pieces of information: • • • • control code Ns (number-sent variable) P/F bit (poll/final bit) Nr (number-
Features Common to Bit-Synchronous Protocols • For ABM data-link protocol: • • Nr Control Field The primary/combined station sets the P bit to 1 in command frames to solicit a response or sequence of response frames from the remote secondary/combined station. F bit is set to 1 by a secondary/combined station to indicate a response frame sent in reply to a command with the P-bit. Number-received variable.
Features Common to Bit-Synchronous Protocols Control Field Figure B-4. Frame-Sequence Acknowledgment Secondary Primary Nr 0 0 0 0 Ns 0 1 2 3 Ns 4 5 6 7 0 Ns 0 1 2 Nr 4 4 4 Ns 3 4 5 Nr 1 1 1 Nr 3 3 3 3 3 010 I-Frame Control Field An I-frame transfers data between two stations.
Features Common to Bit-Synchronous Protocols Control Field The control field of an S-frame contains the following parameters: • • • • Control code (bit 0 = 1, bit 1 = 0) Command/response code (supervisory message code) Poll/final bit Nr In an S-frame, the control code that identifies the frame is 2 bits instead of 1. The Ns parameter is unnecessary because supervisory frames are unnumbered. Ns is replaced by a two-bit command/response code.
Features Common to Bit-Synchronous Protocols Control Field U-Frame Control Field A U-frame provides additional link-control functions. The control field of a U-frame contains the following parameters: • • • Control code (bit 0 = 1, bit 1 = 1) Command/response code (unnumbered message code) Poll/final bit In a U-frame, the control field is similar to that of an S-frame, except that there is no Nr parameter.
Features Common to Bit-Synchronous Protocols Information Field Table B-2. U-Frame Command/Response Codes U-Frame Category Command Recovery responses Frame reject (FRMR) Other commands Exchange identification (XID) Nonreserved 0-3 Other responses Exchange identification Request disconnect (RD) Nonreserved 0-3 Information Field The information field, if present, follows the control field. The most common function of the information frame is to hold the data being transmitted.
Features Common to Bit-Synchronous Protocols Mode-Setting Commands EnvoyACP/XF formats some U-frame commands as a result of procedure calls; in other cases, you must format the command by specifying the appropriate value in the first byte of the message control word (MCW). Additional information on the MCW is provided with the READ, WRITE, and WRITEREAD procedure call descriptions in Section 4, System Procedure Call Specifics for EnvoyACP/XF.
Features Common to Bit-Synchronous Protocols Recovery Command (RSET) Recovery Command (RSET) U-frames provide only one recovery command, RSET. Only combined stations (ABM) use RSET; NRM stations do not use RESET. A combined station transmits the reset (RSET) command to reset the number received variable (Nr). The RSET command clears all frame-rejection conditions except for an invalid Nr condition in the addressed combined station.
Features Common to Bit-Synchronous Protocols U-Frame Responses U-Frame Responses U-frame responses are categorized according to function: U-Frame Responses Category Responses Responses to mode-setting commands and status requests UA, DM, RIM Responses to informationtransfer commands UI Responses to recovery commands FRMR Responses to other commands XID, RD Responses to nonreserved Commands Nonreserved 0-3 Responses to Mode-Setting Commands and Status Requests The secondary/combined station tra
Features Common to Bit-Synchronous Protocols Unnumbered Information-Transfer (UI) Responses Your application issues a CONTROL 14 procedure call to direct EnvoyACP/XF to transmit a RIM frame. Unnumbered Information-Transfer (UI) Responses The UI response transfers an information field to a primary/combined station without affecting the number sent (Ns) and number received (Nr) variables. An information field may be present.
Features Common to Bit-Synchronous Protocols Nonreserved Responses Your application directs EnvoyACP/XF to transmit an RD response by issuing a CONTROL 18 procedure (see the CONTROL procedure in Section 4, System Procedure Call Specifics for EnvoyACP/XF). Nonreserved Responses Your application can use four nonreserved responses to reply to the four nonreserved commands. These nonreserved command/responses allow you to implement your own particular, system-dependent functions.
Glossary $ZZWAN. The process name for the WAN Manager subsystem that configures, starts, manages, and monitors the WAN I/O processes through the SCF product module. ABM. Asynchronous Balanced Mode. A mode of communications within the ADCCP protocol whereby two combined stations communicate on a point-to-point link. Either or both stations can issue commands to set up or dissolve the link. During data transmission, the stations function as peers. This mode is also used by the HDLC protocol. ADCCP.
CONFTEXT Glossary host-resident communication processes. CLIP software implements the specific communications protocols, such as SDLC or HDLC. CONFTEXT. The main configuration file that contains all the hardware descriptions applicable to your Tandem system. control field. The field following the address field in a bit-synchronous frame. It contains bit-encoded commands and responses and can also contain frame sequence numbers.
full-duplex Glossary full-duplex. A method of serial communications in which the data flow between two points can occur in both directions simultaneously. Guardian. An environment available for interactive or programmatic use with the Tandem NonStop Kernel. Processes that run in the Guardian environment use the Guardian system procedure calls as their application program interface. half-duplex.
multipoint Glossary multipoint. A data-link configuration in which one station is designated as the supervisor and controls all communications over the link. The other stations are designated as tributaries. nonswitched. A line configuration that provides a permanent path between two stations. This path can be a privately owned cable or a dedicated path leased from a common carrier. It is generally a leased line. NRM. Normal Response Mode.
ServerNet WAN concentrator Glossary ServerNet WAN concentrator. A six-port communications line concentrator for the Himalaya S-Series. It replaces all of the earlier WAN controllers, such as the 3604, 3605, 3650, and the 6100 communications controllers. SCF. Subsystem Control Facility. A Tandem product that is used to configure, control, and collect information about Tandem data communications subsystems.
zero-bit insertion Glossary zero-bit insertion. A method of distinguishing other fields from the flag field in a bitsynchronous frame. The only field where six successive 1 bits may occur is the flag. In all other fields, EnvoyACP/XF on the transmitting end automatically inserts a 0 bit after five successive 1 bits. The EnvoyACP/XF on the receiving end automatically strips the added 1 bits.
Index A ABM protocol 2-1/2-15 Abort B-2 Accepting incoming frames ABM 2-11 NRM 3-17 Access read/write 1-5 shared 1-5 Activating a line ABM 2-10 NRM 3-12 ADCCP-ABM See ABM ADCCP-NRM See NRM Address default ABM 2-1 general B-2 extended ABM 2-6 ANSI ADCCP 3-24 general B-2 NRM 3-3/3-4 procedure calls 4-9 station lists 3-21 verification ABM 2-5/2-6 HDLC 2-5/2-6 NRM 3-3 ADDRESSSIZE modifier 2-6, 3-3 Alternate transmission 3-10 ANSI ADCCP extended address format 3-24 Application process interface ABM 2-4 NRM 3-2
D Index Command DISC 3-26 link-level 2-2 response codes 4-21 RSET B-11 Command-response codes Message Control Word 4-21 Configuration ABM 2-1 overview 1-7 Connections, establishing 1-10 Contention resolution 2-2 Continuous polling 3-19 Control field ABM 2-6 extended 3-4, B-2 general B-2 NRM 3-4 P/F bit B-4 of a data link 1-8, 3-13 Control code B-4 CONTROL procedure and opening a data link 1-8 general 4-1, 4-2/4-5 NRM 3-26, 3-33 NRM Secondary 3-27, 3-28 SABME 2-14 Count retry count variable 3-7 Cyclic redu
F Index Establishing a data link (continued) overview 1-8, 1-10 SABME example 2-14 Extended address field ABM 2-6 ANSI ADCCP standard 3-24 general 4-9, B-2 NRM 3-3 Extended control field ABM 2-6 overview 1-11, B-2 F Features ABM protocol 2-1 NRM protocol 3-1 FILE GETINFO procedure 4-1 FILE GETINFOBYNAME procedure 4-1 Filenum parameter 1-5 File-system procedures descriptions 4-1/4-22 overview 1-2/1-3 Flag B-1 Flags parameter 1-5, 1-11 Format control field B-4 flag sequence B-1 station list 3-21, 4-7 Frame
L Index I/O (continued) nowait (continued) READ requests 1-11 WRITE requests 1-11 WRITEREAD requests 1-11 queuing ABM 2-11 NRM 3-17 wait opening the line 1-5 I/O requests 3-17 Line ready considerations (continued) timeouts 1-9 Link establishment IBM loop controller 3-14 NRM 3-13 standard 3-13 Link-level commands 2-2 Link-level responses, ABM 2-3 Logical Disconnect State ABM 2-3/2-4 NRM 3-26, 3-27 L M L1RETRY 3-7 L2RETRY 3-7 LDS ABM 2-3/2-4 NRM 3-26, 3-27 Limited polling 3-19 Line capabilities ABM 2-5
N Index N Nonreserved commands B-11 Nonreserved responses B-14 Nonresponding station list, NRM 3-21 Nonswitched lines 1-9 Nonswitched multipoint 3-46/3-49 Nonswitched point-to-point 3-43/3-45 Normal Response Mode (NRM) 3-1/3-49 See also NRM Nowait I/O HDLC 1-6 multiple pending 1-6 overview 1-5 READ requests 1-11 WRITE requests 1-11 WRITEREAD requests 1-11 Nr variable B-5 NRM protocol 3-1/3-49 Ns variable B-4 Number of retries ABM 2-7 NRM 3-6 O Offline state ABM 2-3/2-4 overview 1-9 OPEN procedure ABM 2-5
Q Index Q Queuing I/O requests ABM 2-11 NRM 3-17 R RD 3-27, 3-28, B-13 READ procedure and nowait I/O 1-10 general 4-1, 4-10/4-13 NRM 3-30 Recovering from errors A-5 REJ ABM 2-9 NRM 3-12 Reject See REJ Reject, selective See SREJ 3-12 Request Disconnect 3-27, 3-28 Request initialization mode 3-13 Responses link-level 2-3 polling 3-19 Retries ABM 2-7 NRM 3-7 retry count variable 3-7 RIM 3-13, B-12 RSET B-11 S SABME 2-14 SDLC error handling 3-29 link establishment 3-14 multipoint supervisor 3-39 multipoint
T Index Station combined, definition 1-3 primary or secondary 1-3, 3-3 Station address NRM 3-3, 3-21/3-24, 3-46 SDLC 3-21, 3-46 Station addressing 2-2 Station index entry number 3-21/3-24 MCW 3-16 Station list creating 3-15 format 3-23, 4-7 nonresponding 3-21 SDLC 3-21 Station management 3-32 Switched lines 1-9 Synchronizing open requests 1-5 S-frame control field B-6 general B-4 NRM 3-16 Transmission NRM 3-15 Tributary stations 3-21/3-24 TRNSLENGTH modifier 3-11 TRNSOFFSET modifier 3-11 Troubleshooting,
W Index W Wait I/O 1-5 WRITE procedure and nowait I/O 1-10 general 4-2, 4-19/4-22 NRM 3-33 WRITEREAD procedure and nowait I/O 1-10 general 4-2 NRM 3-33 X XID command B-11 response B-13 Z Zero bit insertion B-2 EnvoyACP/XF Application Programming Manual– 132179 Index- 8
