Abnormal Termination Of Printer Operation; Copy Considerations; Chaining And Error Recovery In 3270 Ipds Mode; Ipds Ack/Nack Sequence In Dsc Mode (Channel-Attached) - IBM 6400 Programmer's Reference Manual

Abnormal Termination of Printer Operation

Any of the following causes rejection of the transmission with a sense equals op
check and cause the control unit to send an abort to the addressed printer:

Copy Considerations

The printer is not available for an operator-initiated copy operation when in IPDS
mode.
If a BSC Copy command is received when in IPDS mode, IPDS mode terminates
and the BSC Copy operation occurs.
Note: It is required that an unordered page be contained within a chain.

Chaining and Error Recovery in 3270 IPDS Mode

A chain is a unit of error recovery. At the end of the chain, the printer delays
sending operation-complete to the control unit until all the received data prints.
To make certain that all deferred printing completes, a chain of IPDS structured
fields should end in the home state. The printer forces IPDS into the home state,
if necessary, to force deferred printing to occur when a chain terminates.
If chaining is not used, each transmission should end in the home state. If
necessary, the printer forces entry into the home state.

IPDS ACK/NACK Sequence in DSC Mode (Channel-Attached)

When using IPDS print operations, the printer can have inbound ACK/NACK data
to send to the host application. Inbound data may result from an Acknowledge
Request required by a prior outbound transmission or from an error condition to
be reported.

Not Recommended NACK Sequence for Printers

When the printer operates in the DSC (channel-attached) mode with IPDS, and
the printer has inbound data to send, the following sequence is not
recommended:
1. The host application receives an Attention from the printer notifying the
2. The host application issues a Read Modified to the printer.
3. The printer sends the NACK to the host application.
4. The host application issues an Erase/Write WCC equals Reset to the printer.
Receipt of a data chain structured field indicating continue or end when not
•
in chain state
Receipt of a data chain structured field indicating begin when already in
•
chain state
Receipt of any 3270 command except BSC Copy, Write Structured Field,
•
Erase Write (WCC equals Reset), or Erase Write Alternate (WCC equals
Reset) when in the chain state
Receipt of a Write Structured Field command that does not contain a data
•
chain structured field when in the chain state.
application that inbound data is available.
This ends IPDS mode.
IPDS for Control Units
Appendix B. Summary of IPDS for Control Units
181