AM3270/TR3271 Reference Manual

6 TR3271 Subdevice Protocols

086705 Tandem Computers Incorporated 6–1

This section discusses the TR3271 implementation of:

The CRT protocol

The PTP protocol

What Are They? The TR3271 level 4 protocols are subdevice-specific. Each subdevice is assigned one of

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

For instructions about adding and configuring TR3271 subdevices, refer to the SCF

Reference Manual for AM3270 and TR3271.

Details of the CRT

Protocol

TR3271 subdevices that are assigned the CRT protocol expect data buffers passed from

an application process to contain text formatted as if the data had come from a 3270

terminal. TR3271 does not examine the contents of outbound data. TR3271 adds

communication-related characters such as STX, ETB, ETX, BCC, and device address

characters to outbound data and deletes communications characters from inbound

data.

Message Format—

Outbound Data

For outbound data, the buffer is passed by the application to the host. CRT adds the

appropriate leading control characters before passing the message.

Figure 6-1. CRT Protocol Message Format—Outbound Data

019

Text (Optional –

Depends on AID)

Write Count

Passed by the Application

Text

Sent to the Host

For outbound data, TR3271 expects the buffer to contain only the text portion of the

message. This includes the Attention ID (AID) byte and, depending upon the AID

byte, a cursor position followed by optional buffer address/text groups.