6100 ADCCP Programming Manual

Setting Line Parameters
Writing Applications that Use ADCCP/X21
5–2 069225 Tandem Computers Incorporated
Setting Line Options After your application has opened the line, your application may need to set either
ADCCP line-configuration options or X.21 line options if they are not set for your
application or have changed due to a previous (1) SET CONFIGURATION or (80) SET
X.21 CONFIGURATION Request. (Your application can check the configuration by
issuing a (2) FETCH CONFIGURATION or (81) FETCH X.21 CONFIGURATION
request to the protocol module.)
Setting ADCCP Line
Options
You define ADCCP line options in the SYSGEN configuration file when you install an
ADCCP/X21 line. If you specified AUTOCONF, the line-configuration options are
automatically downloaded from the host whenever ADCCP/X21 is downloaded.
Normally, your application should not need to change any of these parameters.
However, if your application does need to change the ADCCP line configuration, your
application makes a WRITEREAD call with the (1) SET CONFIGURATION request.
See “Setting Line Options” in Section 4 for a description of how to set line options
using a WRITEREAD call.
Setting X.21 Line Options Most of the X.21 line options are set to default values that reflect CCITT
recommendations. The options are automatically downloaded from the host when
ADCCP/X21 is loaded into the LIU. You do not specify the X.21 line options in the
SYSGEN program, nor can you change them with the Communications Management
Interface (CMI) utility. The default values in the X.21 configuration block can be
modified only by an application program; that is, your application must call
WRITEREAD with the modified values contained in a (80) SET X.21
CONFIGURATION request.
If the ADCCP/X21 line is using a circuit-switched service, your application must issue
a WRITEREAD call with a (80) SET X.21 CONFIGURATION request in which the
CIRCUIT-SWITCHED parameter is set to 255. See Section 6, “Requests and
Responses,” for a description of the (80) SET X.21 CONFIGURATION request.
Preparing to Receive
Asynchronous
Messages
Before the X.21 link is started, your application should issue a READ call so that it can
receive asynchronous line quality reports. See “Preparing to Receive Asynchronous
Messages” in Section 4 for a description of how your application should handle
asynchronous messages from the protocol module.
Starting the X.21 Link After your application has opened the line and set any necessary configuration
parameters, your application must start the link. To start the link, one application
makes a WRITEREAD call with the (6) START OPERATION request. The response to
the request depends on whether the line is a switched or leased line:
Switched ADCCP/X21 enters a quiescent state, signaling “DTE not ready.”
ADCCP/X21 immediately returns a (6) START OPERATION response.
Leased ADCCP/X21 signals “DTE ready.” If the DCE is ready, ADCCP/X21 sets
circuit c to ON and begins to transmit an idle sequence. The (6) START
OPERATION request finishes when the DCE sets circuit i to ON and the
link enters the data transfer state (state 13).