ZCOM Tables and Data Structures
Physical Terminal Tables
PTTXLB - Pointer to next PTT on low priority list linkage
As for PTTXLA above, except that the linkage pertains to the low priority transmit queue.
PTTXQB - Low priority transmit buffer queue
The low priority queue is operated in a similar manner to the high priority queue. Data on this queue is processed only after all express and high priority data has been processed. Note that requests on this queue are subject to the unacknowledged and port transmit limits.
PTTXQC - Unacknowledged transmit buffer queue
This queue contains the buffers from PTTXQA/B after they have been transferred to the interface card, and until they have been acknowledged as sent (or aborted) by the Mux interface card.
PENDG_TXREQ - Next request of $DATA in unack’d transmit queue
This field is used internally by the ZCOM subsystem.
PTPZLK - ZLU of next PTT on this port
Contains the ZLU number of the next terminal which is on the same Mux interface and port as this terminal. These ZLU numbers form a circular list of terminals on the same port. Field PTLIST forms the same circular list, but contains the physical terminal table memory address.
PTDRST - Terminal status
The terminal status is maintained by the driver in this field. The status change requests from application programs are updated in this field after they are successfully passed to the interface card. The driver uses this value to reset the terminal status on the Mux interface after a powerfail or reset.
The content of this field is as follows:
Figure | Terminal Status Field PTDRST |
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| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| EN | AC | UP | AV |
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IN - Terminal has been initialized (ZCOM_PTDRST_INT)
EN - Terminal is enabled (ZCOM_PTDRST_ENB)
AC - Terminal is active (ZCOM_PTDRST_ACT)
AV - Terminal is available for use
Chapter 3 | 71 |