Xerox 4215 Reference Manual page 213

Orders
XEROX MRP FAMILY COAX COMMAND REFERENCE
Orders accepted by the Xerox MRP Family coax printers are
operations that control printing and mode changing. The PCIA
bytes X'0016'—X'0017' specify the type of order the printer is
required to perform. The first byte (X'0016') contains the order
and the second byte (X'0017') contains any applicable parameters
for that order. The following are valid orders:
01 Abort
02 SSA—System Status Available
03 Print processing
05 Load translate tables (ignored)
06 DSC query (ignored)
07 DSC load structured field (IPDS) (ignored)
For any other orders, the 4220/MRP or 4230/MRP coax printer
returns the 'Order Reject' and 'Order Complete' responses to
the host system.
Abort
On receipt of an abort order, the Xerox Family MRP coax printers
terminate the current order and then respond with an 'Order
Complete' in the status byte (byte 'X0000').
This order has no parameters, so the abort order does not use
PCIA byte X'0017.'
System Status Available (SSA)
The SSA order allows the host control unit to change the Print
mode. If the printer is in SCS mode, this order also allows a
request for either PA1 or PA2 action by the host.
Refer to table D-3 for the parameter byte (PCIA byte X'0017')
codes accepted for this order. If these parameters are incorrect,
an 'Order Reject' response is returned to the host system.
Print order processing
This order causes printing of the message buffer while taking the
following into account: the Print mode (PCIA byte X'0017'), the
message starting address (MSA), and the message length (ML)
bytes in the PCIA.
The MSA (PCIA bytes X'0012'—X'0013') identifies the position of
the first byte of data in the print buffer. If the MSA value is
outside print buffer limits, the Xerox MRP Family coax printers
immediately return 'Order Reject' and 'Order Complete'
responses to the host system.
The ML (PCIA bytes X'0014'—X'0015') plus MSA-1 defines the
position of the last byte of data in the buffer. If ML is zero, the
Xerox MRP Family coax printers return an 'Order Complete'
response to the host system without an error condition and
without printing anything.
COAX COMMUNICATIONS BUFFER
D-7