ACC Programmer's Reference Guide

70 Chapter3
ZCOM Tables and Data Structures
Physical Terminal Tables
PTTXLX - Pointer to next PTT on the express list linkage
This linkage (containing the physical terminal table address) is used to
link together physical terminals on the Mux which have messages
queued on the express transmit queue. This field is NULL if the terminal
is not on the list. It is initialized to NULL by TTGEN and is maintained
by the LDM and DAM.
PTTXQX - Express transmit buffer queue
This queue contains the express transmit requests waiting to be sent. It
also contains the terminal configuration (zcntl)requests.Whena
message has been transferred to the card, the buffers are moved to t he
unacknowledged transmit buffer queue. Once the buffer has been
acknowledged as sent or flushed by the card it is removed from the
unacknowledged queue and returned to t he sending program (if
requested by the program).
The express transmit queue is designed for passing critical control
(protocol dependent) data to the terminal. In general, none of the normal
queue limit mechanisms apply to requests on this queue. Normal user
data should NEVER be placed on this queue. An example of appropriate
requests would be an X.25 Reset request or X.25 Expedited data.
Requests on this queue are always processed first, regardless of any
transmit limits that may have been reached.
PTTXLA - Pointer to next PTT on the high priority list linkage
This linkage (containing the physical terminal table address) is used to
link together physical terminals on the Mux which have messages
queued on their high priority transmit queue. This field is NULL if the
terminal is not on the list. It is initialized to NULL by TTGEN and is
maintained by the LDM and DAM.
PTTXQA - High priority transmit buffer queue
This queue contains the high priority transmit requests waiting to be
sent. It also contains the terminal configuration (zcntl)requests.The
data on this queue is processed only after all express transmit data has
been processed. When a message has been transferred to the card, the
buffers are moved to t he unacknowledged transmit buffer queue. Once
the buffer has been acknowledged as sent or flushed by the card it is
removed from the unacknowledged queue and returned to the sending
program (if requested by the program). Note that requests on this queue
are subject to the unacknowledged and port transmit limits.