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C.3. RS-232C/RS-422A Protocol
C-11
H5: Protocol logic
The factory setting is 0.
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 10K bytes. The factory-set value is 6 meaning
60K bytes.
☛ Since DTR/DSR protocol is not used with the RS-422A standard, select a parameter
value other than 0, 1, or 2 for the H5 setting when using the RS-422A interface.
PRESCRIBE IIe FRPO D0 command
The PRESCRIBE IIe FRPO D0 command is provided to allow manipulating XON/XOFF when an error
has occured on the serial interface. The following table summarizes the error status corresponding
to different D0 values.
Parameter value Meaning
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
Serial interface error
error not handled error handled
Timing of XON transfer to
host while Ready or Waiting
XON sent every 3-5 seconds D0 = 0 (default) D0 = 1
XON not sent D0 = 10 D0 = 11