ACC X.25 Protocol User's Guide

ZX25D X.25 Protocol Driver
Virtual Circuit Definitions
Chapter 354
APD This bit is used to control how inbound data packets
which have the D-bit set, should be acknowledged and
when definite write completion status messages are
returned for transmitted messages which have the
D-bit set. If this bit is zero, then inbound data packet
are automatically acknowledged (RR’d) by the ACC
X.25 firmware and write completion status (definite) is
received when outbound data messages are RR’d at
level 2. If this bit is set to one, application end-to-end
acknowledgment is selected. Inbound data messages or
message fragments are not RR’d automatically by the
firmware and outbound data messages receive write
completion (definite) status only after a level 3
acknowledgment (RR) has been received. When setting
this bit to one, special application programming is
required! See the section on “D-Bit Handling” in
Chapter 4, X.25 Application Programming, for a
description of the application programming rules.
WARNING Using end-to-end acknowledgments with the
D-bit set in data messages can severely reduce
the maximum achievable throughput on a VC.
INTC This bit is used to control how confirmations are
handled for inbound interrupt data packets. If this bit
is zero, then inbound interrupt data packets are
automatically confirmed by the ACC X.25 firmware. If
this bit is set to one, application handling of interrupt
confirms is selected. Inbound interrupt data messages
are not confirmed automatically by the firmware.
When setting this bit to one, special application
programming is required! See the section on “Receiving
and Confirming Interrupt Data” in Chapter 4, X.25
Application Programming, for a description of the
application programming rules.