6100 ADCCP Programming Manual

Application Tasks
Writing Applications that Use ADCCP
4–20 069225 Tandem Computers Incorporated
MODE SET
One or more applications make WRITEREAD calls with the MODE SET request, until
a request has accounted for every station on the station list. A single request can set
the mode for more than one station. No two requests (no two applications) should
specify the same station.
If the local station is a primary station, the request causes ADCCP to send a mode-
setting command (for example, SNRM) to the remote station; a UA response from the
remote station completes the request.
If the local station represents one or more secondary stations, the request causes
ADCCP to put the specified station in either of two modes:
SIM if the station must receive a SIM command from the primary.
DISC if the station must receive another mode-setting command.
The MODE SET request finishes immediately. When the local station has received and
acknowledged a mode-setting command from the remote primary station, the mode-
setting frame completes a RECEIVETEXT request.
If the local station is combined, the application issues a MODE SET request to get out
of DEAD mode; it may also request ADCCP to send a SABM command to the remote
station. If the remote station will not be sending a SABM command, then an
application in the local station must issue the MODE SET SABM request. (In
asynchronous balanced mode, at least one station must send a SABM command.) The
request finishes when either a UA or a SABM frame arrives from the remote station.
RECEIVETEXT
In some cases, the ADCCP protocol module delivers mode-setting commands and
responses to an application. For this reason, one application should make a
WRITEREAD call with the RECEIVETEXT request. (Only one application should
make the RECEIVETEXT request; otherwise, you cannot predict which application will
receive data.)
A primary station normally knows when the mode has been set because the
completion of a MODE SET request sets the mode. If, however, the remote station
responds with a RIM instead of a UA in response to a (67) MODE SET request,
ADCCP delivers the RIM to the application to complete a RECEIVETEXT request.
The application must then issue a MODE SET request with a SIM to initialize the
station. If the primary receives a RIM in response to the (67) MODE SET request, the
request fails and an indication is returned in the response that a RIM was received.
After acknowledging a mode-setting command for a secondary station, the ADCCP
protocol module delivers the command to one application. When a RECEIVETEXT
finishes with a notice of the mode-setting command, the application knows that the
mode-setting sequence has occurred on the line. (Thus I-frame traffic is permitted if
the sequence was a SNRM, SARM, and so on; I-frame traffic must end if the sequence
was DISC.)