IPDS for Control Units
Recommended NACK Sequence for Printers in DSC Mode
(BSC-A tta c h ed )
1. The host application receives an Attention from the printer notifying the
application that inbound data is available. The NACK structured field is sent
inbound with the Persist bit active in the flag byte.
2. Any further IPDS data received is ignored by the printer until Step 3 is
completed.
3. A valid IPDS command is received with a length less than 256 with the ARQ
flag active. The NACK structured field is sent a final time, without the Persist
flag bit active. The NACK reply sequence is now complete.
Unlike printers that do not support the Persistent NACK sequence, the printer
remains in IPDS mode with IPDS in Home state.
4. If the NACK was due to a printer IR or EC error, the printer returns an IR or
EC status response on the next 3270 command.
Appendix B. Summary of IPDS for Control Units 187
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