gtps2m0z | ACF/SNA Data Communications Reference |
TPF mapping support builds and formats data streams from application to terminal and from terminal to application. Input messages from 3270 devices contain both control characters and text. Mapping support deletes the control characters and arranges the text in an application compatible format. Conversely, as application-created output messages consist only of text, mapping support inserts the control characters necessary to display the message on a particular 3270 device. Applications receive input messages in AMSG format.
Users are responsible for coding applications that interface properly with TPF mapping support. For input messages, mapping support is used to delete control characters; for output messages it is used to insert control characters. Output messages need control characters inserted before the ROUTC macro is issued.
In bracket communication mode, operators of 3x74/3276-attached terminals may send a message only after receiving an output message with the change direction indicator set. In contention mode, messages may be sent at any time. Therefore, host applications are expected to set the change direction indicator (in the RCPL), thereby controlling bracket communication. TPF ensures the change direction indicator is set when applications release saved input messages.
See 3270 Data Stream Programmer's Reference for more information on the operation of 3270 devices.