Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols

EnvoyACP/XF Application Programming Manual–132179

3-15

Link Establishment with IBM SDLC Loop Controller

Transmitting NRM Commands

You can use the CONTROL procedure to send NRM commands (SNRM, SNRME,

SIM, and DISC) to control the Data Terminal Ready (DTR) signal, and to set your

station to either a Receive Ready (RR) or Receive Not Ready (RNR) condition. A

CONTROL request completes when EnvoyACP/XF transmits the specified

command/signa or when EnvoyACP/XF sets the specified RR/RNR condition.

EnvoyACP/XF Control of the P/F Bit

EnvoyACP/XF automatically controls the setting of the P/F bit in NRM, and sets the P/F

bit under any of the following circumstances:

•

No additional frames are queued to be sent.

•

Window size has been reached.

•

Supervisor detects a timeout error.

Defining the Station List in a Multipoint Environment

All multipoint configurations require a station list:

•

For a supervisor station, the station list specifies the station addresses of all tributary

stations in the network.

•

For a tributary station, the station list specifies the station addresses to which that

station responds.

Figure 3-4. Link Establishment with IBM Loop Controller

Note. Allowing the application program to control setting the P/F bit may interfere with the

normal flow-control operations.

044

Tributary Stations

IBM SDLC

Loop Controller

SNRM

(T1Timeout)

SNRM

Tandem NonStop System

Primary/Supervisor Station