How The Host Determines Screen Sizes - IBM 3708 Description

Configuring the Terminal Table:
Each terminal table (TUT jUDT) may specify that
multiple 3270 Model 2, 3, 4, and 5 screen sizes are supported by the terminal. If the
SET MODE SEQUENCE (see "Customization Section" on page 4-69) for a certain
screen size is specified in the table, then that screen size is supported. If no SET
MODE SEQUENCEs are defined, only Model 2 emulation is supported for the
terminal.
Configuring the Port:
The 3270 Model Emulation option on the C123.2 port
definition screen defines the largest screen supported by the port. Valid input for
this option is 2, 3, 4, or 5. The default value is 2.
If operating mode is defined for protocol enveloping only or device class is defined
for printers or keyboard printers, the 3708 treats any value other than 2 as invalid
for the 3270 Model Emulation option.
SeHlng Up the Terminal:
The 3708 requires the terminal to be properly configured
to allow the 3708 to select screen sizes and set the terminal's character generator to
correspond to the model size being emulated. Depending on the terminal, the ports,
pages, windows, line allocation, and character generation setup must all be enabled
to support the screen size being emulated. The terminal setup is the responsibility of
the terminal installer or the terminal user. The 3708 does not check to confirm the
terminal is set up for any of the large or default screen sizes.
Specifying Sizes With the BIND:
The BIND must specify a screen size (24 x 80, 32 x
80, 43 x 80, or 27 x 132). If a size is not specified, then 24 x 80 is assumed.
When the BIND is received, the 3708 checks the port configuration and the screen
definitions in the terminal table for the size indicated in the BIND. If the terminal
does not support that size or if the port is not configured for it, the 3708 rejects the
BIND with a negative response code (X'0821').
How the Host Determines Screen Sizes
The 3708 does not support a READ QUERY REPLY or any other structured field
command that allows the host application to interactively determine the
characteristics of the attached display. Therefore, screen sizes must be statically
defined at the host. For example, screen size information can be placed in
LOGMODE tables, CICS Terminal Control Tables (TCTs), or IMS Terminal
Control Tables.
The host can set the screen size in one of the following ways:
• The user can invoke the correct BIND by entering a logon message that tells the
host what screen size to use. For example, the user may type
LOGON TSO M5
to
invoke a Model 5 BIND image from the application.
• Since each port on the 3708 corresponds to a particular LU, the host application
may simply transmit, for example, a Model 5 BIND to a given LU. This
requires that all the terminals attached to that particular port support Model 5
emulation. If the terminal does not support a Model 5 screen size, the 3708
rejects the host BIND with a negative sense code of X' 0821' .
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IBM 3708 Description