gtpi1m54System Installation Support Reference

Tape Display Setup

The tape display user exit, UXTD, is called to set up message displays for tape devices supported by TPF 4.1. A message is displayed until it is changed by another Load Display (LDD) command or until the cartridge is physically unloaded. Therefore, UXTD is called at mount, dismount, and tape switch time (to reset the display if the tape is not unloaded).

Note:
UXTD will only be activated if the tape device is supported on TPF 4.1.

The message display is set up in the SETUP subroutine, which can be modified. This should be the only code modified in UXTD. On return from SETUP, the calling routine will issue a Load Display command to display the messages set up by this routine.

UXTD is called by the following segments:

Input

The following registers are used by the SETUP subroutine:

R1
Pointer to LDD data area DSECT

R5
TSTB/1 (Tape Status Table/Section 1) address

R6
TSTB/2 (Tape Status Table/Section 2) address

R7
Return address

The contents of R7 through R15 are expected to be unchanged on return from SETUP.

Data Structures

DSECT LDDAREA maps the data portion of the LDD CCW that will be sent to the tape device. This area consists of the following fields:

The 2 message areas, LDDMSG1 and LDDMSG2, are each 8 bytes. Both are initialized to zeros when SETUP gets control.

Table 5. The Byte Arrangement for Message Display

Message 1 Message 2 Display
Zeros Zeros LDD not issued
Nonzeros Zeros Message 1 only
Zeros Nonzeros Message 2 only
Nonzeros Nonzeros Alternating Message 1/Message 2