ACC X.25 Protocol User's Guide

ZX25D X.25 Protocol Driver
Virtual Circuit Definitions
Chapter 3 53
ACK If set, the application will confirm incoming CALLs
using zx25callacc(). If clear, then the X.25 protocol
driver will automatically accept an inbound call by
sending an X.25 level 3 Call Accept protocol packet.
Note that if this bit is set, the CNT bit should also be
set so that the application is notified that an inbound
call has arrived.
VCT Virtual circuit type - 0=SVC, 1=PVC.
IN If set, then incoming Calls are allowed.
CLL This bit controls the actions taken on a PVC/SVC when
it is enabled or on recovery of an X.25 link. If set, an
outgoing Call Request is automatically issued for a
SVC when the SVC ZLU is enabled or the X.25 link is
restarted. For PVCs, a Reset Request is automatically
issued when the PVC ZLU is disabled. If the CLL bit is
clear, no action is taken.
NLL If set, the Call address (X.121) for this SVC is
automatically set to NULL when the call is cleared.
This address is kept in the Physical Terminal Table
ptcnfg field. For inbound calls it specifies that calling
address that will be accepted in an inbound call. For
outbound calls placed as a result of an SVC enable or
when the called address was not supplied to the
zx25callout() routine, the address in the ptcnfg field is
used as the calling address in the Call Request packet.
If the address is automatically set to NULL, then an
inbound call from any calling address will be
acceptable. If this bit is clear, the Call address in ptcnfg
is not set to NULL when the call is cleared. Note that
for inbound calls, the calling address is automatically
placed into the ptcnfg field. For outbound calls, the
called address is placed into the ptcnfg field.
DEA If set, the VC ZLU is deactivated after every received
message. A deactivated VC will generate an X.25 level
3 RNR when an inbound data packet is received.
Sending a zcntl() to activate the VC will generate an
X.25 level 3 RR packet and allow one more inbound
data packet to be received. If this bit is clear, the VC
ZLU will only be deactivated through explicit zcntl()
calls by the application.