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APPENDIX C
SLMC804 CONTROLLER
COMMAND SUMMARY
The Atari SLMC804 Page Printer Controller functions as a translator
between the parallel DMA bus
interface
of the Atari ST Computer and
the serial video interface of the xerographic printer engine. The
SLMC804 is an intelligent controller, providing device-independent
command interpretation and control of printer operations.
Bus communication follows a defined host-initiated dialog sequence
consisting of a COMMAND PHASE, DATA OUT PHASE, and STATUS
PHASE. Data transfers are asynchronous and follow a Data Request/
Acknowledge handshake protocol, with one byte of data transferred
during each handshake. Note that the controller contains a two-byte
FIFO which is loaded prior to the transfer of a new block of data.
The host can interrogate the controller for a list of configuration
parameters which is received during an EXTENDED STATUS PHASE.
The host can also send the controller a parameter list during an
EXTENDED COMMAND PHASE.
COJtl.
m and Definitions
Commands are dispatched to the page printer controller via a six-
byte Command Descriptor Block. Note that a delay is required
between consecutive Command Descriptor Blocks to allow time
for the controller to respond.
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