Networking and Data Communications Library AM3270/TR3271 Reference Manual Product Version Release ID Edition Print Date Part Number Abstract C30/D10 C30.09/D10.00 March 1993 086705 This manual describes the AM3270 and TR3271 Access Methods. It is intended for applications programmers and system managers responsible for programming for, using, or managing systems and networks.
Document History Edition Part Number Product Version Release ID Print Date First Edition Second Edition 082451 086705 A00 C30/D10 N/A C30.09/D10.00 September 1985 March 1993 New editions incorporate any updates issued since the previous edition. Release ID Note Release ID specifies the release in which the software functions described in an edition are first available on a standard SUT (site update tape). Copyright Copyright © 1993 by Tandem Computers Incorporated. All rights reserved.
New and Changed Information New and Changed This revision of the AM3270/TR3271 Reference Manual describes the following changes Information and enhancements to these processes and to the documentation: Interface information: Additional D-series support for SCF has been added to AM3270 and TR3271. CMI is not supported for AM3270 and TR3271 for D-series. CUP is supported for C-series for AM3270 and TR3271, but only for the 6202 controller.
New and Changed Information New and Changed Information iv 086705 Tandem Computers Incorporated
Contents Preface xi Notation Conventions Section 1 xiii Bisync Protocols—Concepts and Terminology What are Bisync Protocols? 1-1 Standard Bisync Communication—How It Works The Message Block 1-3 Transmission Control Characters 1-5 EBCDIC and ASCII Control Characters Bisync Procedures 1-8 Error Checking (Block Checking) Polling and Selecting 1-9 Transparent Mode 1-13 For More Information Section 2 1-2 1-7 1-8 1-14 Overview of AM3270 and TR3271 What Are AM3270 and TR3271? 2-1 When Are They Used? 2-1
Contents Using Multiple-Level Access Methods 3-6 Level 1—Bisync Driver 3-7 Level 2—Multipoint Supervision 3-7 Level 3—Request Processor 3-10 Level 4—Subdevice Protocols 3-10 Error Handling 3-11 Section 4 AM3270 Subdevice Protocols What Are They? 4-1 Details of the ITI Protocol 4-1 Message Formats 4-1 Subdevice Information 4-2 Applicable File-System Procedures 4-2 CONTROL 11 and 12 (Modem Connect or Disconnect) READ Request 4-3 SETMODE Functions 4-3 SETPARAM 3 (BREAK Indication) 4-4 WRITE Request 4-6 WR
Contents Details of the PRT Protocol 4-17 Message Format 4-18 Applicable File-System Procedures CONTROL 1 Operation 4-19 WRITE Request 4-19 Error Handling 4-19 4-18 Details of the QUO Protocol 4-20 Communication With Quotron Devices File-System Procedures 4-21 Section 5 4-20 A Closer Look at TR3271 Overview 5-1 Three TR3271 Modes Examples 5-2 5-1 Subdevices 5-3 Configuration and Control of Emulated Subdevices Level 4 Protocols 5-3 TR3271-Specific Operations 5-3 Implementation Caveats 5-4 Multiple-Ad
Contents Section 6 TR3271 Subdevice Protocols What Are They? 6-1 Details of the CRT Protocol 6-1 Message Format—Outbound Data 6-1 Message Format—Inbound Data 6-2 Applicable File-System Procedures 6-2 Error Handling 6-8 Details of the PTP Protocol 6-8 Sample Configuration 6-9 What About File System Requests? 6-10 Communication Loss 6-10 Typical Pass-Through Configuration 6-11 Appendix A AM3270 and TR3271 Controller and Device Tables Controller/Device Addresses A-1 Address Examples A-2 Glossary Glossar
Contents Figure 4-5. PRT Protocol Message Format 4-18 Figure 5-1. TR3271 Standard Configuration Figure 5-2. TR3271 Pass-Through Configuration Figure 6-1. CRT Protocol Message Format—Outbound Data Figure 6-2. CRT Protocol Message Format—Inbound Data Figure 6-3. TR3271 Process Configuration Figure 6-4. Pass-Through Configuration 5-2 5-3 6-1 6-2 6-9 6-11 Tables Table 1-1. Bisync Transmission Control Characters (Page 1 of 2) 1-6 Table 1-1.
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Preface This manual describes the access methods AM3270 and TR3271, which provide application programs with links to IBM mainframes and IBM 3270-family terminals and printers. The information in this manual applies to: 3650/6100 CSS for D- and C-series releases Non-6100 CSS environments for C-series releases only. How This Manual is This manual is divided into three parts: Organized Sections 1 and 2 describe bisynchronous (bisync) protocols in general and give an overview of AM3270 and TR3271.
Preface Your Comments Invited SCF Reference Manual for AM3270 and TR3271 Lists and explains SCF command use for AM3270 and TR3271 subsystems. Includes TRACE and sense/status byte information. Your Comments Invited xii The Reader Comment Card, which you will find at the end of this manual is your opportunity to tell us what you want in future editions. Many of the improvements you see in Tandem manuals are the result of suggestions from our readers. Please take a moment to fill it out and send it in.
Notation Conventions The following list summarizes the conventions for syntax presentation in this manual. Notation Meaning UPPERCASE LETTERS Uppercase letters represent keywords and reserved words; enter these items exactly as shown. Lowercase italic letters represent variable items that you supply. Brackets enclose optional syntax items. A group of vertically aligned items enclosed in brackets represents a list of selections from which you can choose one or none. Braces enclose required syntax items.
1 Bisync Protocols— Concepts and Terminology This section explains: Basic bisync concepts, terms, and procedures. Types of message formats. Bisync control characters. Standard procedures, such as polling and selecting. For introductions to Tandem’s AM3270 and TR3271 access methods see Section 2, “Overview of AM3270 and TR3271 Access Methods.
Bisync Protocols—Concepts and Terminology What are Bisync Protocols? Figure 1-1 compares bisync and async character framing. Figure 1-1. Two Methods of Character Framing Stop Character 1 2 Start 3 4 5 6 7 8 Asynchronous (Start/Stop) Synchronization Window D C E 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 SYN SYN Char Buffer B C C Bisynchronous 001 Standard Bisync Communication— How It Works In bisync protocols the bit and character synchronization occur at the beginning of each message.
Bisync Protocols—Concepts and Terminology What are Bisync Protocols? 3. Data Block Transmission: The message block is then sent. The beginning of the message or control sequence is located by finding an appropriate control character following the SYNs. These would be control characters that are defined as beginning a block of data or a control sequence, such as SOH or STX. 4.
Bisync Protocols—Concepts and Terminology What are Bisync Protocols? Figure 1-2. Basic Message Block SYN SYN SOH Header STX Text ETX BCC Data Flow Legend Control characters used to identify header, text, and trailer include: SOH Header STX ETX BCC = Start of Header. Transmitted before the header characters. Optional. = Header Text. Optional. = Start of Text. Transmitted before the first data characters. = End of Text. Terminates a message block starting with SOH of STX. = Block Check Character.
Bisync Protocols—Concepts and Terminology Control Characters Elements of a Message Block These are the elements of a message block: Header Identified by a Start of Header (SOH) character at the beginning and a Start of Text (STX) at the end. Contains one or more characters identifying the sending and/or receiving location, which also may be referred to as an address. Text Identified by a preceding Start-of-Text (STX) control character.
Bisync Protocols—Concepts and Terminology Control Characters Table 1-1 lists the bisync transmission control characters, and describes their use and the appropriate response, if any. Table 1-1.
Bisync Protocols—Concepts and Terminology Control Characters Table 1-1. Bisync Transmission Control Characters (Page 2 of 2) Bisync Control Character (Mnemonic) EBCDIC and ASCII Control Characters Function Action and Response(s) ITB Intermediate block character TTD Temporary text delay Separates long message blocks into sections for error detection without causing a reverse of transmission direction. Indicates block check is next, and resets counter to zero.
Bisync Protocols—Concepts and Terminology Bisync Procedures Table 1-2.
Bisync Protocols—Concepts and Terminology Bisync Procedures For the EBCDIC code set, error checking is based on a cyclic redundancy check (CRC), and is called CRC-16. The CRC is a division performed by both the sending and receiving stations. The numeric binary value of the message is divided by a constant, the quotient is discarded and the remainder is transmitted as a two-byte block check character sequence.
Bisync Protocols—Concepts and Terminology Bisync Procedures ENQ—Used to indicate both poll and select. The type of request is determined by the encoding of the address characters. ACK and NAK—Used in two ways: In response to a previously transmitted data block, and as a response to a select request (ACK0 only). NAK applies to a poll but not to a select.
Bisync Protocols—Concepts and Terminology Bisync Procedures The polled 3270 CU remains selected at the completion of a poll operation so that the application can issue a WRITE, ERASE/WRITE, ERASE/WRITE ALTERNATE, COPY, or EAU command without having to reselect the 3270 CU and its subdevice. (These refer to commands sent inside the data stream, rather than to Guardian 90-specific commands.) To terminate the general poll, an RVI issued to the 3270 CU forces an EOT response.
Bisync Protocols—Concepts and Terminology Bisync Procedures The cluster controller manages the link between the supervisory station and the tributaries on that line, which reduces response time from the network. The cluster controller handles all of the messages to and from the stations on its link. As a result, the supervisory station (or CPU, or front-end processor) needs to poll only each cluster controller, and not each of the individual stations attached to it.
Bisync Protocols—Concepts and Terminology Bisync Procedures Figure 1-4 shows the basic message sequences in polling and selecting. Figure 1-4.
Bisync Protocols—Concepts and Terminology For More Information are not interpreted as control sequences such as “end-of-transmission.” However, even during transparent operation, some form of line control is still required. When transparent mode is turned on, any subsequent control characters are interpreted as raw data only. Characters that are meant to be interpreted as control characters are preceded by a data link escape (DLE) character.
2 Overview of AM3270 and TR3271 This section introduces: The Tandem access methods AM3270 and TR3271 The subsystem components What Are AM3270 and AM3270 and TR3271 are Tandem’s implementations of IBM’s 3270 BSC protocols. TR3271? The AM3270 Access Method supports communications with IBM 3270 terminals that are connected to one or more byte-synchronous 3271 cluster controllers. Under this access method, one data communications process controls a single byte-synchronous line.
Overview of AM3270 and TR3271 Level 4 Protocols Note PTP is a trademark of Tandem Computers Incorporated. CICS is a trademark of IBM Corporation. CICS, when used in this manual, refers to products, technologies, architectures, processes, standards, or APIs originated by IBM Corporation. The term “CICS server” or “CICS application,” for example, when used in this manual, refers to a server or an application that will interoperate with an IBM API.
Overview of AM3270 and TR3271 Level 4 Protocols CRT display mode (CRT) protocol Printer mode (PRT) protocol Quotron (QUO) protocol AM3270 and TR3271 subdevice protocols are specified through SCF, not SYSGEN; therefore, command interpreters accessing 3270 terminals may be brought up only after executing SCF commands. Note The Communications Management Interface (CMI) can also be used for C-series releases, but it has less functionality than SCF, and Tandem recommends that you use SCF.
Overview of AM3270 and TR3271 Level 4 Protocols CRT Protocol This is the basic mode of operation for 3270 terminals and printers. When a terminal is configured in this mode, AM3270 adds the communication control characters on output of the message and strips communication control characters on input. The application program is totally responsible for the actual screen format control (such as field protection or highlighting). A 3270 terminal controller may send input data in 256-byte blocks.
3 A Closer Look at AM3270 This section includes: Figures that illustrate typical configurations Descriptions of subdevice access Lists of AM3270-specific operations and file-system procedures Descriptions of the AM3270 process levels Overview Examples Section 2 described and compared the AM3270 and TR3271 access methods. This section describes aspects of AM3270 that are specific to this access method only. The examples in this section show AM3270-specific configurations.
A Closer Look at AM3270 Subdevices The following figure shows how AM3270 might be used in a pass-through configuration. Figure 3-2. Example of AM3270 Pass-Through Configuration 3270 Devices and Controller t1 Tandem NonStop System AM3270 3274/3274 (PTP) t1 t2 Comm Line x1 (PTP) t2 (PTP) IBM Compatible Host TR3271 Comm Line x2 t3 t3 (PTP) (CRT) 007 Subdevices Configuration and Control Note Subdevice Access This section discusses the ways in which AM3270 accesses subdevices.
A Closer Look at AM3270 AM3270 Specific File System Operations and Procedures AM3270 makes it possible for the application process to issue requests to terminals without concern for low-level communications-related line characteristics. AM3270-Specific Table 3-1 summarizes the file-system procedures that can be used by an application File-System process as requests to AM3270. Operations However, note that some of the level 4 subdevice protocols do not allow the use of all of the procedures listed below.
A Closer Look at AM3270 AM3270 Specific File System Operations and Procedures Figure 3-3 illustrates the poll operation. Figure 3-3. Poll Operation CALL OPEN CALL READ AM3270 adds the subdevice to the poll list.
A Closer Look at AM3270 AM3270 Specific File System Operations and Procedures Select/Write Operation When an application process calls the WRITE procedure, AM3270 will select the appropriate terminal or printer. Outbound text contains the appropriate communication characters (STX,ESC,ETX), which are inserted prior to the transmission of text to the subdevice. Each message is written to a device as one WRITE operation.
A Closer Look at AM3270 AM3270 Product Environment AM3270 Product Table 3-2 lists some of the features of AM3270 as they apply to Tandem NonStop Environment systems and to Tandem NonStop systems with a 3650/6100 CSS or a 3605/6105 controller. The 6202 controller is supported for C-series releases only. Table 3-2. AM3270 Product Environment Function 3650/6100 CSS Maximum Devices/Line—253* ASCII/EBCDIC Character Code User-defined Translation Maximum Line Speed—19.
A Closer Look at AM3270 AM3270 Product Environment subdevice protocol (one of the level 4 protocols) is invoked to provide further processing of the request. Level 4—the subdevice protocols—provide the file-system interface to the subdevices. Level 1—Bisync Driver Level 1, the bisynchronous driver, initiates physical I/O to the controller (or LIU— 6100 CSS) and handles completions of events such as interrupts and timeouts.
A Closer Look at AM3270 AM3270 Product Environment Figure 3-5.
A Closer Look at AM3270 AM3270 Product Environment Figure 3-6.
A Closer Look at AM3270 AM3270 Product Environment ASCII/EBCDIC Line Code An application process need deal only with the ASCII character set. For example, if the line code is EBCDIC, the CLIP in a 3650/6100 CSS can be configured through SCF to automatically translate from ASCII to EBCDIC (and the reverse). This can also be accomplished through system generation parameters.
A Closer Look at AM3270 AM3270 Product Environment A fully-qualified subdevice name consists of the line name and the subdevice name specified by the user when the subdevice was added. A subdevice name is in the form of #name, where the # character has significance to the file system. The following is an example of a fully-qualified name that would be defined for the OPEN procedure (in the following, b is a blank): INT .
4 AM3270 Subdevice Protocols This section discusses the following AM3270 subdevice protocols: ITI, for interactive terminals PTP, for pass-through functions CRT, for standard CRT display mode PRT, for printers What Are They? The AM3270 level 4 protocols are subdevice-specific: Each subdevice is assigned one of these modes when it is added to the system and configured. For instruction about adding and configuring AM3270 subdevices, refer to the SCF Reference Manual for AM3270 and TR3271.
AM3270 Subdevice Protocols Details of the ITI Protocol Subdevice Information The following information pertains to the AM3270 ITI protocol in the 3650/6100 CSS environment: The BREAK function is simulated by the PA1 key. The end-of-file operation (CTRL-Y character) is simulated by the PA2 key. The EOF! is displayed on the screen.
AM3270 Subdevice Protocols Details of the ITI Protocol CONTROL 11 and 12 (Modem Connect or Disconnect) The CONTROL procedure performs device-dependent I/O operations. A CONTROL 11 means wait for modem connect; a CONTROL 12 means disconnect the modem. Even though a CONTROL 11 or 12 is meant for use in a dial line environment, note that dial lines are not supported in AM3270.
AM3270 Subdevice Protocols Details of the ITI Protocol The following SETMODE functions are used to set certain terminal characteristics for this protocol: SETMODE 8 Set transfer mode—default is conversational. parameter 1 0 1 SETMODE 11 Set BREAK ownership—default is 0. parameter 1 0 disable BREAK. cpu,pin = enable BREAK. parameter 2 0 1 normal mode, any type file access is permitted (default). BREAK mode, only BREAK-type access permitted.
AM3270 Subdevice Protocols Details of the ITI Protocol filenumber the file number provided by OPEN—this is an INT:value. function function code is 3; will set or fetch parameters for BREAK handling—this is an INT:value. param array a list or string as required by function—this is passed by reference (INT:ref:1). param count the number of bytes contained in param array—this is an INT:value.
AM3270 Subdevice Protocols Details of the ITI Protocol cpu,pin = enable BREAK. buf[1] terminal access mode after BREAK is typed. 0 normal mode (any file type access is permitted). 1 BREAK mode (only BREAK-type file access is permitted). Where buf[2] and buf[3] are the two words of the 32-bit tag. This tag is saved by the I/O process handling the 3270 terminal.
AM3270 Subdevice Protocols Details of the PTP Protocol Table 4-1 lists some of the error conditions that could occur during READ and WRITE operations. Table 4-1. ITI Protocol READ/WRITE Errors Operation/Error Number Description Action/Indication READ 171 No response. The cluster controller for the device did not respond. Text sent by the device was NAKed by AM3270 until the retry count was exhausted. Check the cluster controller for an error condition.
AM3270 Subdevice Protocols Details of the PTP Protocol Figure 4-2. Pass-Through Protocol Example 3270 Devices and Controller t1 AM3270 (PTP) t1 Comm Line t2 (PTP) t3 TR3271 Cluster Controller (CRT) x1 t2 (PTP) Comm Line Host x2 t3 (PTP) User Program 013 As illustrated in Figure 4-2, AM3270 terminals t1 and t2 are connected to corresponding emulated subdevices x1 and x2 on the TR3271 side and have their data “passed through” to the host.
AM3270 Subdevice Protocols Details of the CRT Protocol Loss of Communication If communication between line handlers in separate systems on a network is lost, no special action is taken. If the failure was due strictly to communication loss, the two line handlers continue when communication is restored. If the failure was due to a system failure/reload, the SCF CONNECT command can be performed again, using the reloaded system as the local system.
AM3270 Subdevice Protocols Details of the CRT Protocol Message Format— Outbound Data Figure 4-3 shows the format for outbound CRT messages. Figure 4-3.
AM3270 Subdevice Protocols Details of the CRT Protocol Figure 4-4 shows the format for inbound CRT messages. Figure 4-4.
AM3270 Subdevice Protocols Details of the CRT Protocol outstanding READ requests (whose sizes may be substantial), it is possible that data buffer space will quickly be exhausted. Instead of issuing a normal READ, the application issues a CONTROL 22 (called a forerunner to a READ), which in effect requires file system buffer resources to be committed only when AM3270 has data from the subdevice.
AM3270 Subdevice Protocols Details of the CRT Protocol General Information When a text message is received or a line error occurs, the CONTROL request completes by returning a file-system error 0 if the read was successful; otherwise, it returns a specific error number. If the file-system error is 0, a READ must be issued as soon as possible to pick up the input buffer.
AM3270 Subdevice Protocols Details of the CRT Protocol The format is: CALL SETMODE (filenumber, 53, param1, param2, lastparams); filenumber INT:value, the file number for the subdevice as returned by the OPEN. 53 INT:value, the SETMODE value for receiving 3270 status. param1 INT:value, 0 1 disable status receive. enable status receive. param2 INT:value, the response ID. This 16-bit quantity is provided as identification by the requesting process.
AM3270 Subdevice Protocols Details of the CRT Protocol For a more detailed discussion of sense and status bytes (which are displayed by using the SCF command STATUS SU), including a table listing sense/status bytes, refer to the SCF Reference Manual for AM3270 and TR3271. Example of Use An application may pass information back and forth between subdevices on an AM3270 line and a TR3271 line.
AM3270 Subdevice Protocols Details of the CRT Protocol SETMODE 59 Operation SETMODE 59 returns the actual count of bytes read as a result of a CONTROL 22 (two-step READ) completion. The format is: CALL SETMODE (filenumber, 59, , , params); filenumber INT:value, the file number returned by the OPEN for the subdevice. 59 INT:value, the SETMODE number for obtaining the actual count of the bytes read. params INT:ref:2, must be provided and returns: params[0] params[1] actual number of bytes read. 0 (zero).
AM3270 Subdevice Protocols Details of the PRT Protocol Error Handling The errors returned by AM3270 are generally the result of receiving no response or an improper response from the physical device. Status is solicited by AM3270 using a specific poll. Errors returned to the application process are the result of a translation performed by AM3270 based upon the actual status that was received from the device. Table 4-2 lists some of the error conditions that could occur during READ or WRITE operation.
AM3270 Subdevice Protocols Details of the PRT Protocol Message Format Figure 4-5 shows the PRT protocol message format. Figure 4-5. PRT Protocol Message Format Text Line to be Written Passed by the Application Write Count S T X E S C C M D W C C Text Line to be Written E M E T X B C C Printer Orders Added by AM3270 016 The printer protocol takes an output buffer containing pure text and adds the appropriate 3270 printer orders to it. The buffer is then written to the subdevice.
AM3270 Subdevice Protocols Details of the PRT Protocol CONTROL 1 Operation The CONTROL procedure is used by printer subdevices for forms control operations. Line printer devices attached to a cluster controller may have forms operations performed on them by application processes or Tandem subsystems.
AM3270 Subdevice Protocols Details of the QUO Protocol Table 4-3 lists some of the error conditions that could occur during WRITE operations. Table 4-3. PRT Protocol WRITE Errors Operation/Error Number WRITE 123 WRITE 171 WRITE 172 Details of the QUO Protocol Description Action/Indication Device Busy. Indicates that a WRITE operation is in progress. No Response. When the device was selected, the cluster controller did not respond. Improper Reply.
AM3270 Subdevice Protocols Details of the QUO Protocol File-System Procedures Although the QUO protocol is transparent to the AM3270 I/O process, including the QUO protocol module, request handling for QUO subdevices is substantially different from request handling for CRT subdevices. The CRT protocol module of the AM3270 I/O process handles READ and WRITE requests using a single queue.
5 A Closer Look at TR3271 This section includes: An overview of the TR3271 communications subsystem Examples of TR3271 process configuration Details about subdevice access, configuration, and control A list and explanation of the level 4 (subdevice) protocols TR3271-specific operations and file system procedures A list and details about TR3271’s four process levels Overview The TR3271 Tributary Access Method provides communications with IBM mainframes where the Tandem system appears to be one or more 3270
A Closer Look at TR3271 Overview For specifics about configuring and using TR3271 subdevices, refer to the SCF Reference Manual for AM3270 and TR3271. Examples The following two figures show two typical TR3271 configurations, one standard and one pass-through. For a more complex version of these figures, refer to the figure in Section 6, “TR3271 Subdevice Protocols.” Standard Configuration Figure 5-1 shows a TR3271 process emulating a cluster controller with two terminals, #X1 and #X2.
A Closer Look at TR3271 TR3271-Specific Operations In pass-through mode, no formatting or deformatting of the buffer is performed by either AM3270 or TR3271. All text is passed on a whole-message basis, which means that AM3270 gathers all blocks of a multiblock message before sending it to TR3271. Figure 5-2 shows a typical TR3271 pass-through configuration. In the illustration terminals t1 and t2 have their data passed through AM3270 and TR3271 to the host. Figure 5-2.
A Closer Look at TR3271 TR3271-Specific Operations Implementation Caveats In a network environment it is not feasible to implement a full software simulation of a 3270-family controller and its devices; therefore, TR3271 is more loosely coupled with its emulated devices. Responding to an Application’s READ Due to this loose coupling, TR3271 does not wait until the application’s READ has completed before returning the appropriate response (such as ACK) to the host.
A Closer Look at TR3271 TR3271-Specific Operations Data Buffers TR3271 does not checkpoint data buffers. For example, if data is received and acknowledged, and the TR3271’s processor fails before the data can be transferred to the application process, the data will be lost. Multiple-Address Versus Single-Address Lines In the 3650/6100 CSS environment, the monitoring of subdevice addresses is a function that is handled within the CSS, thereby removing the task from the Tandem CPU.
A Closer Look at TR3271 TR3271-Specific Operations Depending on the value for the SYSGEN INITSTATUS modifier, TR3271 must respond to the host; otherwise, the host will no longer use the emulated terminal. In this situation, TR3271 listens for polls and selects that are meant for the emulated device. Any poll that is received causes an EOT to be returned by TR3271 to the host. The EOT indicates that the device has no data to send.
A Closer Look at TR3271 TR3271-Specific Operations Read-Modified TR3271 response to a read-modified command from the host depends on the specification of TR3271 macro modifiers, which are set during SYSGEN: READMODAFTERPOL NOREADMODAFTERPOL If NOREADMODAFTERPOL is specified, any read-modified command from the host is rejected (NOREADMODAFTERPOL is the default).
A Closer Look at TR3271 TR3271-Specific Operations TR3271 issues a READ I/O to receive one block. The block is moved into the message buffer. TR3271 sends an ACK and issues another I/O to receive the next block of the message. If a block is received, it is appended to the end of the previouslyreceived block in the message buffer. TR3271 checks the 3270 command within the block to verify that it is “chainable” to the previous block (see “Functional Limitations” below).
A Closer Look at TR3271 TR3271-Specific Operations The following is an example that illustrates how the Reset MDT is handled by a 327x control unit and TR3271. In the examples, assume that a two-block message is sent. Block #1 has a Reset MDT bit set to 0, and block #2 has its Reset MDT bit set to 1. Also, block #1 contains fields where the MDT bit in the field attribute has been set by the host.
A Closer Look at TR3271 Summary of Applicable File-System Procedures For your information, the obsolete caveats are: EOT delay Handled within the 3650/6100 CSS, so no longer relevant to the CPU. Conversational replies Particularly in the area of buffer allocation, this applies only to TR3271 in a non3650/6100 environment. Although conversational replies are also supported for TR3271 in the 3650/6100 environment, the actual function is handled within the CSS itself.
A Closer Look at TR3271 Using Multiple-Level Access Methods the host with the text. When all text has been sent or a nonrecoverable error occurs, TR3271 completes the WRITE request to the application. TR3271 Product Table 5-2 lists some of the features of TR3271 as they apply to Tandem Guardian 90 Environment systems with a 3650/6100 CSS. Table 5-2. TR3271 Product Environment TR3271 3650/6100 CSS Maximum Devices/Line—253* ASCII/EBCDIC Character Code Maximum Line Speed—19.
A Closer Look at TR3271 Using Multiple-Level Access Methods Level 4—the subdevice protocols—provide the file system interface to the subdevice. Note I/O Interface Procedure (IOP) Levels 3 and 4 describe Tandem’s implementation of these protocols, rather than describing an International Standard. The I/O interface procedure (IOP) provides the communications path between GUARDIAN 90 and TR3271. Requests to TR3271 are performed through the IOP.
A Closer Look at TR3271 Using Multiple-Level Access Methods Level 2 Protocol Level 2 provides the operations required to sequence a communication line through the bisynchronous multipoint tributary protocol. Since the host controls the line, requests from applications do not have any direct effect on line state. Data may be written to the host only when the host polls the line. READ requests are satisfied when the host chooses to select the subdevice and send data to it.
A Closer Look at TR3271 Using Multiple-Level Access Methods plus the required additional communications characters. When the host selects a subdevice with a READ request pending, TR3271 requests a buffer equal in size to the record size that was defined for the communications line during system generation. When the application’s request has been completed due to successful transfer or an unrecoverable error, the buffer is returned to the pool.
A Closer Look at TR3271 Using Multiple-Level Access Methods Error Handling Error conditions that occur at various levels are evaluated by TR3271 which determines if the error can be handled at the level where errors are detected, at another level, or by the application process. Retries are performed either according to the BSC protocol or by the application process.
6 TR3271 Subdevice Protocols This section discusses the TR3271 implementation of: The CRT protocol The PTP protocol What Are They? The TR3271 level 4 protocols are subdevice-specific. Each subdevice is assigned one of these modes when it is configured and added to the system. For instructions about adding and configuring TR3271 subdevices, refer to the SCF Reference Manual for AM3270 and TR3271.
TR3271 Subdevice Protocols Details of the CRT Protocol As illustrated in Figure 6-1, TR3271 adds an STX at the beginning of all blocks. It also adds the control unit and device address at the beginning of the first block and an ETB at the end of all blocks except the last, after which an ETX is added, followed by a BCC. For Figure 6-1, assume that all data fits into one block.
TR3271 Subdevice Protocols Details of the CRT Protocol standing READ requests (whose sizes may be substantial), it is possible that data buffer space will quickly be exhausted. Instead of issuing a READ, the application issues a CONTROL 22 (called a forerunner to a READ), which in effect requires file-system buffer resources to be committed only when TR3271 has data from the host.
TR3271 Subdevice Protocols Details of the CRT Protocol Considerations When a text message is received or a line error occurs, the CONTROL completes with a file-system error of 0 (zero) if the read was successful, or a file-system error of some specific number if otherwise. If the error is 0, a READ should be issued immediately to pick up the data buffer (a SETMODE 59 could precede the READ—see below; also see “SETMODE Functions” in this section).
TR3271 Subdevice Protocols Details of the CRT Protocol SETMODE Functions The call to SETMODE is as follows: CALL SETMODE (filenumber , function [, parameter 1 ] [, parameter 1 ] [, last params ]) SETMODE functions applicable to this protocol are summarized below. SETMODE 30 allows file-system requests to complete in any order. (Normally, file-system requests are completed in the order in which they are issued on any particular file number.
TR3271 Subdevice Protocols Details of the CRT Protocol clear, that status bit will remain as whatever TR3271 currently has as status (see the status parameters below). Manipulation of status bits by the application must be performed carefully because arbitrary changes may cause problems at the host, for example, an unknown combination of status bits or loss of status when status is expected.
TR3271 Subdevice Protocols Details of the CRT Protocol SETMODE 59 Detail CALL SETMODE (filenumber, 59, , ,params); filenumber an INT:value—is the file number returned by the OPEN for the subdevice. 59 an INT:value—is the SETMODE number for obtaining the actual count of the bytes read. params is passed by reference (INT:ref:2), must be provided, and returns: params[0] actual number of bytes read. params[1] 0 (zero).
TR3271 Subdevice Protocols Details of the PTP Protocol block at a time. When the last block has been acknowledged by the host, TR3271 completes the WRITE request to the application process. If the host issues a general poll, and status other than device busy is set, TR3271 returns a status message instead of message text. If the host issues a specific poll, and any status is pending, TR3271 returns that status instead of text. In neither case is any pending WRITE request completed.
TR3271 Subdevice Protocols Details of the PTP Protocol Sample Configuration Figure 6-3 shows a TR3271 process emulating a cluster controller with two terminals, X1 and X2. Variations on this figure appear in Section 5, “A Closer Look at TR3271,” showing two simpler configurations. Since Figure 6-3 portrays a much more complex configuration, you may find it helpful to compare the figures. Figure 6-3.
TR3271 Subdevice Protocols Details of the PTP Protocol The SCF CONNECT command is used to join X1 to T2. Subdevice T3 is configured in ITI mode because a command interpreter will be started on this terminal. The command interpreter IN and OUT files are $AM.T3. Subdevice P1 is a printer configured in PTP mode and is controlled by AP3. What About File System Requests? To TR3271, a successful CONNECT acts as a combination of an OPEN (EXCLUSIVE) and a READ.
TR3271 Subdevice Protocols Details of the PTP Protocol Typical Pass-Through Configuration Figure 6-4 illustrates a typical pass-through configuration. Figure 6-4. Pass-Through Configuration 3270 Devices and Controller AM3270 TR3271 t1 x1 t1 (PTP) t2 (PTP) Comm Line (PTP) t2 Comm Line Host x2 (PTP) 022 In the above illustration, terminals t1 and t2 have their data passed through AM3270 and TR3271 to the host.
Appendix A AM3270 and TR3271 Controller and Device Tables Controller/Device In Table A-1 the character " is used as the device address to specify general poll. Addresses Table A-1. AM3270 and TR3271 Controller/Device Addresses CU/UNIT Control Unit Poll/Device Poll or Select EBCDIC ASCII Graphic Hex Graphic Hex Control Unit Select EBCDIC ASCII Graphic Hex Graphic Hex 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 sp A B C D E F G H I cent .
AM3270 and TR3271 Controller and Device Tables Controller/Device Addresses Address Examples These are examples of poll and select addresses: SELECT CU2 DA 14 SPECIFIC POLL CU 2 DA 2 GENERAL POLL CU 1 A–2 086705 Tandem Computers Incorporated = = = SS ++ enq BB BB enq AA ““ enq
Glossary 3650/6100 family controller. Programmable controller, such as the 6101/6110 or 3605/6105, that has the following characteristics: 6100 CSS architecture Programmable, down-loaded logic Multiple protocol support Single operations interface (fully reconfigurable online) Dual or single input/output paths Hardware resides in system, input/output cabinet, or standalone cabinet 6100 communications subsystem (CSS).
Glossary CCITT. Comité Consultatif International Télégraphique et Téléphonique (International Telegraph and Telephone Consultative Committee). A standards-setting group for international telephone carriers. CIU . Communications Interface Unit. This is the proper term used for the 3650/6100 family of controllers. There can be two of these dual-ported, programmable I/O controllers in each 6100 CSS or 3650 CSS; the CIUs connect the host with the rest of the 6100 CSS or 3650 CSS.
Glossary CUP. Communications Utility Program. Similar to COUP, it allows online configuration of devices without the need to repeat the system generation process. CUP, however, can only configure dedicated (also called “non-6100” or “nondownloadable”) controllers and their associated subdevices, such as terminals and printers. For lines controlled by AM3270 or TR3271, you cannot configure subdevices using either INSTALL/SYSGEN or DSC/COUP.
Glossary IOP. Input output process. Within the context of the 3650/6100 family of controllers, this type of I/O process is called a CAP (communications access process). LIM. Line Interface Module. Part of the LIU in a 3650/6100 subsystem, the LIM is the actual connection to the communication line. It provides the physical and electrical interface to the outside world. LIU. Line Interface Unit. A component of the 3650/6100 subsystem. Each LIU supports a single communications line.
Glossary RS-232. An industry standard for serial data transmission. It describes pin assignments (for a 25-pin connector), signal functions, and electrical characteristics. RS-232C is the current standard. RTS. Request to send. A signal from the host computer or terminal (DTE) to the modem (DCE) requesting permission to transmit data. Permission is granted when the modem turns CTS to ON. subdevice.
Index 3270 devices connected to Tandem 2-2 6-bit transmission 1-8 6202 controller support 3-6 A Access method components 2-2 Access methods, layered 3-6 ACK0 1-9 Addressing for poll and select 1-9 Addressing, for polling and selection A-1 AID character 4-10 AM3270 Buffer formatting in PTP 4-8 Dial lines not supported 4-3 Error handling in CRT 4-17 Formatting in PTP 4-8 General characteristics 2-1 Interactive environment 4-1 ITI message formats 4-1 ITI protocol 4-1 Level 4 protocols 4-1 OPEN, READ, WRITE 4-8
Index B Basic unit of bisync 1-3 BCC 1-5 Errors 3-10 BCC and error checking 1-8 BCC characters 1-8 Binary-synchronous protocols 1-1 Bisync and async, compared 1-1 Bisync control character equivalents 1-7 Bisync control characters Using 1-6 Bisync manuals 1-14 Bisync transmission 1-1 Bisync, standard operation 1-2 Bisynchronous driver 3-6 Bit synchronization 1-1, 1-2 Block Error checking 1-5 Start of Header (SOH) 1-3 Text 1-3 Trailer 1-3 Block check sequence 1-8 Block checking 1-8 Block length 1-5 Maximum 1
Index Buffer contents, CRT 4-9 Buffer formatting in PTP 4-8 Byte-sync protocols 1-1 C Character framing 1-2 Character synchronization 1-1, 1-2 Character-oriented protocols 1-1 Checking synchronization 1-2 Checksum 1-5 CLIP configuration 3-10 Cluster controllers 1-11, 2-1 CMI support 3-2 Command interpreter, CONTROL commands 4-3 Communication lost, PTP 4-9 Configuration AM3270 3-1 Configuration example, pass-through 4-7 Configuration, joining subdevices in PTP 4-8 Configuring QUO devices 4-21 Configuring su
Index Control unit, sense and status bytes 1-10 Control units supported 2-2 Control units, IBM-equivalents 2-2 Controller addresses A-1 Controller concentrator 2-2 Controller concentrator (Quotron) 2-4 Controllers, cluster 1-11 COPY command, IBM’s in CRT 4-15 CRC-12 1-8 CRC-16 1-8 CRT Error handling 4-17 Error handling using specific poll 4-17 File-system READ 4-11 Message format 4-10 Normal READ 4-13 Passing data buffers 4-9 protocol 4-9 Receipt of status messages 4-13 SETMODE 53 4-13 subdevices 4-9 WRITE
Index E EBCDIC block checking 1-8 EBCDIC line code 3-10 Emulated subdevices 4-8 End-of-block indicator 1-3 ENQ 1-9 EOT 1-9 EOT, when sent 3-4 EOTIFNOREAD 3-4 Error conditions 3-10 List for PRT 4-20 Error conditions, AM3270 3-11 Error conditions, CRT 4-17 Error detection, timeouts 3-10 Error handling for PRT 4-19 Error handling in CRT 4-17 Error handling, AM3270 3-11 Error handling, ITI 4-6 Error handling, PTP 4-9 Errors during READ or WRITE in ITI 4-6 Errors, transmission 3-10 Expand networks 2-2, 2-3 F Fe
Index Front-end processors 1-11 Full-duplex 1-9 Full-duplex lines 1-1 Fully-qualified names, subdevices 3-10 G General poll 1-10 General poll with no pending READ 3-4 H Half-duplex 1-9 Half-duplex lines 1-1 Header Block 1-3 Start of 1-3 Highlighting screens 2-4 I I/O operations, device-dependent 4-3 I/O process decoding 3-7 I/O process interface paths 3-10 I/O, physical 3-7 IBM control units selecting 1-11 IBM control units supported 2-2 IBM COPY command in CRT 4-15 IBM reference manuals 1-14 Interactive e
Index J Joining subdevices 4-8 L Layered access methods 3-6 Level 3, request processor 3-10 Level 4 protocols 3-11 Level 4 protocols, AM3270 4-1 Level 4, subdevice protocols 3-10 Line characteristics, concern for 3-2 Line code 3-10 Line control 1-9 Line control, and transparency 1-13 Line counters, internal for ITI 4-6 Line handler requests in PTP 4-9 Line handlers, PTP 4-8 Line polling Caused by SETMODE 53 4-13 Line printers PRT protocol 4-19 Line sequencing 3-7 Line-level transparency 1-1, 1-13 Links Mul
Index Multi-station links 1-9 Multiblock First and last blocks 1-4 SYN characters 1-4 Multiblock, defined 1-3, 1-4 Multiple point connections 1-9 Multiple-level access methods 3-6 Multiplexing in Quotron devices 4-21 Multipoint connections 1-9 Multipoint supervisor 3-6, 3-7 N Nothing-to-send 1-9 O Odd parity 1-9 OPEN in AM3270 PTP mode 4-8 Operation errors in ITI 4-6 P PA1 key 4-2 PA1 key (simulated BREAK) in ITI 4-6 Pad characters 1-2, 1-3 Padding for sychronization 1-2 Parameter setting and fetching, ITI
Index Polling 1-9, 2-3 Caused by SETMODE 53 4-13 Halted with WRITE request in CRT 4-16 specific 1-11 terminating 1-11 Polling and READ 3-3 Polling and selecting, compared 1-10 Polling, effect of WRITE requests 4-6 Positive acknowledgements 1-1 Printer order EM 4-18 ETX 4-18 Printer protocol 2-4 Printer protocol for AM3270 4-17 Product environment 3-6 Protocol CRT 2-4 Pass-through 4-7 PRT 4-17 PTP described 4-7 QUO 4-21 Protocols CRT 2-2, 4-9 ITI 2-2 Level 4 3-11 PRT 2-2, 2-4 PTP 2-2 QUO 2-2, 2-4 Quotron de
Index PTP Configuration example 4-7 Data transfer 4-8 Error handling 4-9 Joining subdevices 4-8 Protocol described 4-7 PTP protocol 2-3 Q QUO And EOTIFDNOREAD 4-21 And RETRIES 4-21 And RVIIFNOREAD 4-21 Multiple READs and WRITEs 4-21 QUO devices, configuring 4-21 QUO protocol 2-2, 2-4, 4-20 And AM3270 I/O process 4-20 READ and WRITE 4-21 Quotron controller concentrator 4-20 Quotron CU 2-2 Quotron devices 2-4 Multiplexed 4-21 Quotron devices and SYSGEN 4-21 Quotron devices, communicating with 4-20 R READ Inv
Index READ request in PTP 2-3 READ request, response from AM3270 3-7 READ requests 3-7 READ, completing in ITI 4-3 READ, two-step for AM3270 CRT 4-11 READ, two-step in block mode 4-2 READ/WRITE errors, CRT protocol 4-17 Receive mode 1-9 Receive timeout 1-3 Request processor 3-6 Request processor, level 3 3-10 Request-to-send 1-10 Response times 1-11 Retransmission 1-8 Retries 3-10 Retries, maximum 3-10 Retry count 3-4, 3-10 Roll-call polling 1-11 RVI, when sent 3-4 RVIIFNOREAD 3-4 S SCF Status and sense by
Index Sense bytes 4-14 Sequencing communications line 3-7 SETMODE 4-53, 4-54 Causing line polling 4-13 Screen copy in CRT 4-15 SETMODE 53 in CRT 4-13 SETMODE 53, ITI protocol 4-3 SETMODE 54 in CRT 4-15 SETMODE 59 in CRT 4-16 SETMODEs in ITI 4-4 SETPARAM 3 4-4 SETPARAM 3 for BREAK handling 4-5 Setting BREAK parameters 4-4 Six-bit transmission 1-8 Specific poll 1-10, 1-11 CRT error handling 4-17 Specific poll, to solicit status in ITI 4-6 Start of header 1-3 Status and sense bytes, example of use 4-14 Status
Index SYN characters 1-3 SYN SYN characters 1-3 Synchronization 1-1 Checking 1-2 Maintenance 1-2 T TACL 3-2 TACLs on subdevices 4-1 Tandem BSC 2-1 Terminal characteristics, setting in ITI 4-4 Terminal control characters 1-6 TERMNO 3-11 Text, block 1-3 Timeout value, standard 3-10 Timeouts 1-3 Timeouts, error detection 3-10 TR3271 General characteristics 2-1 Pass-through 2-2 Uses 2-2 TR3271, described 2-1 Trailer, block 1-3 Transmission control characters 1-6 Transmission errors 3-10 Transmit timeout 1-3 Tr
Index V VFU operation (CONTROL 1) for PRT 4-19 VRC/LRC 1-8 W WRITE Completing physical write in CRT 4-16 Halts polling in CRT 4-16 Internal line counters 4-6 QUO protocol 4-21 Quotron 4-21 WRITE errors in ITI 4-6 WRITE operations 3-5 WRITE request for PRT 4-19 WRITE request in ITI 2-3, 4-6 WRITE request in PTP 2-3 WRITE request, response from AM3270 3-8 WRITEREAD in ITI 4-6 Index–14 086705 Tandem Computers Incorporated
