Envoy ACP/XF Application Programming Manual

Features Common to Bit-Synchronous Protocols
EnvoyACP/XF Application Programming Manual–132179
B-11
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. A combined station may send
the RSET command as an alternative to a FRMR (frame reject) command if it detects an
invalid Nr.
Your application directs EnvoyACP/XF to transmit an RSET command by issuing the
CONTROL 14 procedure call (see CONTROL in Section 4, System Procedure Call
Specifics for EnvoyACP/XF). This control request completes without error if the remote
station responds with a UA.
When the calling process issues this CONTROL call, any pending WRITE requests not
yet acknowledged by the remote system are completed with a CCL and file-system error
174.
Other U-Frame Command: XID
A primary/combined station can transmit the Exchange Identification (XID) command
to elicit a station identification from the addressed, secondary/combined station. The
XID also can provide the station address of the primary/combined station to the
secondary/combined station.
If the XID provides the station address of the primary/combined station, the address is
included in an optional information field. An ABM station or a NRM station can use this
command. A secondary/combined station responds with an XID response unless a UA
response is pending, a FRMR or RIM condition exists, or the secondary/combined
station is in disconnected mode.
Your application directs EnvoyACP/XF to transmit a XID command by using a WRITE
or WRITEREAD procedure call to place the appropriate value in the first byte of the
MCW.
Nonreserved Commands
Four nonreserved command codes allow you to define special system-dependent
functions.
Your application directs EnvoyACP/XF to transmit a one of these nonreserved
commands by using a WRITE or WRITEREAD procedure call to place the value in the
first byte of the MCW. Use of these specialized commands must be coordinated with the
remote station.