Envoy ACP/XF Application Programming Manual

Normal Response Mode (NRM) Protocols
EnvoyACP/XF Application Programming Manual–132179
3-45
NRM Nonswitched Point-to-Point
The first WRITE call terminates polling. Each WRITE call sends an I-frame.
EnvoyACP/XF controls setting the P-bit because the stations are configured for full-
duplex operation:
PRIMARY SECONDARY
I-Nr(0),Ns(0) ———————————> READ loop accepts incoming
I-Nr(0),P,Ns(1) ———————————> frames. For each AWAITIO
completion, check for CCL
(error), CCE (more frames
to come), and CCG (last
frame.
EnvoyACP/XF acknowledges the two received frames. WRITE requests complete at the
application level. EnvoyACP/XF resumes polling.
<———— [Nr(2),RR,F]
[Nr(0),RR,P] —————————————>
.
.
.
WRITE call sends I-frame.
<———— I-Nr(2),Ns(0) (P/F=0)
WRITEREAD call sends
I-frame and passes the
poll bit back to the
primary.
<———— I-Nr(2),Ns(1) (P/F=1)
Secondary once again
begins monitoring the
line for incoming frames.
EnvoyACP/XF acknowledges
the two frames received
from the secondary and
resumes polling.
[Nr(2),RR,P] —————————————>
EnvoyACP/XF automatically
responds to poll.
<———— [Nr(2),RR,F]
[Nr(2),RR,P] —————————————>
<———— [Nr(2),RR,F]
Application issues a
CONTROL 18,5 request.
DISC —————————————————————> EnvoyACP/XF
station to disconnect
state. The AWAITIO
call for the READ
operation completes
with CCG and with %10
in MCW.<3:7).
Application closes the Application closes the
line. line.