1284 Parallel - QMS 19 User Manual

1284 Parallel

The Centronics parallel interface supports two modes for 1284
bi-directional communication, nibble mode and byte mode:
In nibble mode, bi-directional communication between the printer
and the host is done in nibbles (four bits) with the low order nibble
sent first. A transfer of two nibbles is required for each byte of
information. In byte mode, bi-directional communication between
the printer and the host is done in bytes. The byte mode may be
used by the host device in a DMA (Direct Memory Access) mode
for more efficient operation.
When byte transfer is complete and there is no more data to
transmit, the host may do one of the following:
terminate and return to the compatibility mode.
stay in the HostBusy, Data Not Available phase.
set HostBusy Low, putting the interface into the idle phase.
If there is additional data, the host may do one of the following:
set HostBusy Low, indicating that the host can accept
additional data.
stay in the HostBusy, Data Not Available phase.
terminate and return to the compatibility mode.
Check your host documentation to see if the host is 1284
compatible.
T e c h n i c a l S p e c i f i c a t i o n s
EDNord - Istedgade 37A - 9000 Aalborg - telefon 96333500
Appendix B
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