X25AM Programming Manual

ITI Applications

X25AM Programming Manual—527201-001

2-14

Changing the Terminal Mode with SETMODE

ITI assumes that the remote terminal is in conversation mode when the call is

established. Your application can control the mode by issuing a SETMODE 8

statement as follows:

•

For conversation mode, set SETMODE 8 parameter 1 to 0.

•

For page mode, set SETMODE 8 parameter 1 to 1.

ITI sends the appropriate control sequence to the terminal and the SET PAD

PARAMETER command to the PAD.

The content of the mode-setting control sequence sent to the terminal is controlled with

the SCF subdevice attribute NULLFILL. ON is used for terminals with microcode

revision C and earlier. The default of NULLFILL OFF is for terminals with more current

microcode revisions. The control sequences are as follows:

NULLFILL ON: Conversation Mode = EOT NUL SOH “C” ETX

Page Mode = EOT NUL SOH “B” ETX

NULLFILL OFF: Conversation Mode = EOT PAD SOH “C” ETX

Page Mode = EOT PAD SOH “B” ETX

Terminal Reset

A 6520 or 6530 terminal can be reset from the keyboard with a soft (shifted RESET) or

hard (shifted CONTROL RESET) reset. A hard reset (shifted CONTROL RESET keys)

changes the mode to conversation mode. ITI receives the solicitation control sequence

(ENQ CR) in either case.

ITI terminates all READ and WRITE operations being executed by the application and

returns error 191 (Terminal Reset). If the terminal was in conversation mode, ITI issues

a control sequence for conversation mode and resumes processing. If the terminal was

in page mode, ITI issues a control sequence for page mode and resumes processing.

Optimizing Output Data from 6530 Terminals

When it receives a page mode control sequence, a 653x terminal checks the terminal

configuration menu to determine if packet blocking mode is enabled.

If packet blocking mode is not enabled, data is transmitted from the terminal in blocks

with 256 bytes of data and 4 framing characters. Assume that the L3 window size is 2

and the packet size is 128. The PAD forwards the data as two packets of 128 bytes

and another packet with 4 bytes. Since the window size is 2, the network (ITI) must

respond with an RR before the third packet is sent. The application acknowledges the

three packets with an ACK, which ITI puts in a packet and sends on to the terminal.

Figure 2-5 on page 2-15 illustrates packet transfer without blocking.