AM3270/TR3271 Reference Manual

4 AM3270 Subdevice Protocols

086705 Tandem Computers Incorporated 4–1

This section discusses the following AM3270 subdevice protocols:

ITI, for interactive terminals

PTP, for pass-through functions

CRT, for standard CRT display mode

PRT, for printers

What Are They? The AM3270 level 4 protocols are subdevice-specific: Each subdevice is assigned one

of these modes when it is added to the system and configured.

For instruction about adding and configuring AM3270 subdevices, refer to the SCF

Reference Manual for AM3270 and TR3271.

Details of the ITI

Protocol

A terminal assigned to the ITI protocol is used to run the standard Tandem Advanced

Command Language (TACL). With a TACL running on the subdevice, the terminal

operates in an interactive environment. As a result, it can initiate any kind of

application process operation that is allowed on a normal interactive device (such as

EDIT and FUP).

Message Formats Figure 4-1 shows the two message formats for the ITI protocol.

Figure 4-1. ITI Protocol Message Formats

012

Text Line to

be Written

Write Count

Passed by the Application

Sent to the

Terminal

Controller

Screen

Orders

Text Line to

be Written

The interactive terminal interface protocol takes an output buffer containing pure text

(minus control information) to be written and adds an STX, an ESC, a command, a

write control character, and appropriate 3270 screen orders. An ETX is inserted after

the last text byte, followed by a BCC.