Cabletron Systems CBU-NM User Manual page 105

14.1 Control Link Handshaking
This feature helps to protect against overloading under high levels of
alarm traffic. Without it, if PCNC receives a stream of alarms faster than
it can process them, alarm data will be lost when PCNC's receive buffers
become full.
14.2 Handshaking provisions
The handshaking facility is optional and is enabled or disabled via an
entry in PCNC.INI (see section
handshaking is disabled, to retain compatibility with previous versions.
When it is enabled, the handshaking scheme is designed to operate with
PCNC connected to the master port of a Cabletron port sharer (PSV). It
operates by monitoring the incoming DSR on the control link, together
with the state of PCNC's receive buffer, and producing a resultant DTR
signal as follows:
DSR in (voltage)
Inactive (-ve)
Active (+ve)
Active (+ve)
The 'nearly full' condition is detected when the buffer comes within 500
bytes of being full, whereas the 'plenty of space' condition is detected
when there are 100 or fewer received bytes unprocessed.
80-60100000-02
14 Handshaking
7.8.5
Rx buffer state DTR out (voltage)
Don't care Inactive (-ve)
Nearly full Inactive (-ve)
Plenty of space Active (+ve)
Handshaking
for details). By default,
14–1