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Appendix C Host Computer Interface
RS-232C Protocol
A protocol is a set of rules the computer follows in sending data
to the printer. The RS-232C parameters are stored in battery
backed-up memory. They are indicated on the status page.
They can be changed by the FRPO (firmware reprogram)
command described in the
the CD-ROM supplied with the printer. The parameters and
their identification codes are given below.
H1: Baud rate
Parameter value
12
24
48
96
19
38
57
11
The factory setting is 9600 baud.
H2: Data bits
7 or 8, factory-set to 8.
H3: Stop bits
1 or 2, factory-set to 1.
H4: Parity
Parameter value
0
1
2
3
The factory setting is "None" (0 on the status page).
H5: Protocol logic
Parameter
value
0
Combination of 1 and 3 below
1
DTR/DSR, positive logic
2
DTR/DSR, negative logic
3
XON/XOFF
4
ETX/ACK
5
XON/XOFF recognized only as protocol
The factory setting is 0.
C-4
Programming Manual
provided on
Baud rate
1200
2400
4800
9600
19200
38400
57600
115200
Meaning
None
Odd
Even
Ignore
Meaning
H6: Buffer nearly-full threshold
This is a percentage from 0 to 99. The factory setting is 90.
H7: Buffer nearly-empty threshold
This is a percentage from 0 to 99. The factory setting is 70.
The factory settings of the buffer nearly-full and nearly-
empty thresholds (H6 and H7) are subject to change without
notification.
The gap between the nearly-full and nearly-empty thresholds
allows the computer to send a fairly large amount of data in
a continuous stream.
H8: Received-data buffer size
This is the size of the input buffer, specified in units of 10
Kbytes. The factory-set value is 6, meaning 60 Kbytes.
PRESCRIBE FRPO D0 Command
The PRESCRIBE FRPO D0 command provides control over
XON/XOFF operation when an error occurs on the serial
interface. The following table summarizes the error status
corresponding to different D0 values.
Timing of
XON sent
XON transfer
every 3-5
to host while
seconds
Ready or
XON not sent
Waiting
Serial interface error
Error not
Error
handled
handled
D0=0 (default)
D0=1
D0=10
D0=11
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