Asynchronous Nack In Lu-1 Mode - IBM 6400 Programmer's Reference Manual

IPDS for Control Units
In Figure 31, the host issues an End Bracket with no EDS. The host issues no
Change Direction.
Figure 31. Asynchronous NACK in LU-1 Mode. End Bracket issued after Signal.
Notes:
1. At the end of this sequence, the printer is no longer in IPDS mode nor does
2. If the printer generates an Intervention Required (IR) or Equipment
Synchronous or Non-Intervention Required NACK Sequences in LU-1 Mode: If
the host application sets the Acknowledge Reply (ARQ) field of the flag byte to 1,
the ACKs or NACKs from the printer are synchronous.
Note: Intervention Required (IR) or Equipment Check (EC) NACKs returned as a
result of ARQ equals 1 are treated as asynchronous NACKs. In Figure 32, the
host sends data immediately after the Signal from the printer. The host sends
the Change Direction after the data. In Figure 33 and Figure 34, the host does
not send a Change Direction.
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6400 IPDS
the host read the NACK.
Check (EC) NACK, the printer sends the IR or EC status to the host in the
next transmission. The IR or EC replaces the normal response transmission
from the printer shown in Figure 31 above.