ZCOM Tables and Data Structures

Logical Terminal Tables

LTTYPE - Logical terminal type

The logical terminal type is used to describe the message format expected from the terminal. For screen-type terminals this will identify the terminal as belonging to a class of terminals with the same screen formatting attributes and message delimiters (e.g., IBM.3278 or NCR.501).

LTFLAG - System status flags

Currently the system status flags are used to indicate whether the outbound multiplexing and the inbound multiplexing are enabled.

Figure 3-2 System Status flags

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OM IM

OM - Outward bound multiplexing, ZCOM_LTFLAG_OMX bit

IM - Inbound multiplexing, ZCOM_LTFLAG_IMX bit

Both are set by TTGEN according to the device type specified. These flags may be modified dynamically by use of the zltmx routine call.

LTZMXP - ZCOM address of multiplexing program

This field contains the node, ZLU number, and checksum of the outbound multiplexing program. If the ZCOM_LTFLAG_OMX bit in ltflag is set, the responsible multiplexing program should set up this field with its primary ZLU (via the zset_rcvr routine, mode 2). All out-going messages will then be queued to its primary ZLU.

LTZPRCVR - ZCOM address of primary indirect receiver

This field contains the node, ZLU number, and checksum of the program to receive data messages from an inbound multiplexed terminal. If the ZCOM_LTFLAG_IMX bit in ltflag is set, the system sets up this field on a zset_rcvr (mode 0) call. All incoming messages will be received by the inbound multiplexing program, which will then route the data to the receiver specified in this field.

Chapter 3

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