Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols
EnvoyACP/XF Application Programming Manual–132179
3-32
NRM WRITE Procedure
The example in Figure 3-9 assumes the presence of two tributary stations (address 01
and address 02) and shows the OPTION1 method of I-frame acknowledgment.
NRM WRITE Procedure
In response to WRITE requests, EnvoyACP/XF queues I-frames and unnumbered
command or response frames for transmission. The effect of a WRITE request depends
on the type of station your application is controlling, as follows:
Figure 3-9. Delaying I-Frame Acknowledgment
Type of Station Effect of a WRITE Request
Multipoint supervisor Frames are sent as soon as the link can handle them.
Point-to-point primary Same as Multipoint supervisor, above.
Multipoint tributary Frames remain queued until the supervisor polls the station.
Point-to-point secondary Same as Multipoint tributary, above.
049
Supervisor Station
Tributary Stations
(NR/NS)
01 RR–P
01 I–F
02 RR–P
02 RR–F
01 RR–P
(0)
(0, 0)
(0)
(0)
(1)
1
2
3
4
5
Legend
1 The supervisor station polls tributary station 01 by sending it an RR–frame
with the poll bit set.
2 Tributary station 01 responds by sending back an I–frame with the final bit set.
3 The supervisor station does not immediately acknowledge the I–frame from
station 01, but proceeds to poll tributary station 02.
4 Station 02 does not have any information to send, so it responds by sending
the RR–frame with the final bit set.
5 The supervisor's polling cycle is once again at station 01; the supervisor
sends the RR–frame to station 01 with the poll bit set, and the sequence
number for the frame number received (NR) is increased to 1.