ZCOM Tables and Data Structures

Logical Terminal Tables

LTHLDQ - Sub-packet holding queue

This queue is a holding queue for partial messages to an inbound multiplexed terminal.

LTDHQN - Data holding queues

For use by an application program to store temporary data for each terminal. Only the queue header is stored in these fields, as the data itself is stored in the ZCOM subsystem buffers.

LTUSER - User-maintainable area

The fields in the user-maintainable area may be modified by the zltup call. The area consists of the following fields (up to the end of the terminal table):

LTADDR - Logical terminal address

Holds the logical terminal addressing information needed to recognize the correct logical terminal in a group of multiplexed terminals. This is a 10-byte field, however the multiplexing program may use these bytes according to the specific requirements of the protocol.

LTSTAT - Logical status

Contains the status of the logical terminal. This entry is maintained by a multiplexing program and will remain unaltered for a normal 1:1 terminal.

Figure 3-3

Logical Status Structure LTSTAT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

15

14

13

12

11

10

9

8

 

7

6

5

4

3

2

1

0

 

EN

AC

UP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EN - logical terminal enabled (ZCOM_LTSTAT_ENB)

AC - logical terminal activated (ZCOM_LTSTAT_ACT)

UP - logical terminal up (ZCOM_LTSTAT_UP)

LTCWCT, LTTXCT, LTRXCT, LTERCT - Message and error counters

Allow message counters for control writes, transmit data, receive data, and error events to be maintained by the multiplexing application program, for multiplexed logical terminals.

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Chapter 3