IPDS for Control Units
Inbound Structured Fields
When the printer is in DSC mode with the 3270 data stream, the query reply is
the only structured field sent inbound.
When the printer is in DSC mode with IPDS, Select IPDS Mode and IPDS
acknowledge reply are the only structured fields sent inbound. The printer can
only send a Select IPDS Mode structured field inbound if it has previously
received an outbound IPDS structured field, and a reply is required with the
acknowledge reply structured field. This field can be a STM, an OPC, an ACK, or
a NACK.
Selecting and Terminating IPDS Mode of Operation
An application can select the IPDS mode of operation by sending a Select IPDS
Mode structured field (X
'0F83') at the beginning of each transmission containing
IPDS structured fields. If the application is using data chaining, the select IPDS
mode structured field must follow in the same transmission. A select IPDS mode
structured field must not be sent with a continue or end chain.
The IPDS mode terminates at the end of the transmission containing the select
IPDS mode structured field unless data chaining is in effect.
If the select IPDS mode structured field is preceded by a data chain structured
field indicating Begin, then the IPDS mode remains in effect until the end of a
transmission containing a data chain structured field indicating End is received.
When IPDS mode terminates, the application returns to the base data stream of
3270.
Note: For BSC-attached control units, a transmission is defined as the data
delimited by Select and EOT. For channel-attached control units, a transmission
is defined as the data transferred by a WSF command (that is, a CCW).
Figure 35 shows the DSC data stream modes.
Appendix B. Summary of IPDS for Control Units 179
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