IBM 6400 series Maintenance Manual page 78

Replace any cable that is damaged or fails continuity test. Reconnect all
stacker cables to the CMX controller board, stacker, and stacker control
panel.
021 RECEIVE BUFFER OVERRUN
VERIFY CONFIGURATION
1. The print buffer has overflowed on a serial interface. The printed output may
contain random * (asterisk) characters. Make a configuration printout. Verify that
the printer matches the host serial interface configuration settings for Data
Protocol, Baud Rate, Data Bits, Stop Bits, Parity, Data Terminal Ready, and
Request to Send.
Set printer serial interface parameters to match those of the host.
2. Send a print job to the printer.
If the message appears, go to Communications Failures, page 133.
022 UNIT ADDRESS NOT RECEIVED
CHECK PRINTER ADDRESS
1. Poll timeout on the twinax interface indicating the unit address is not recognized
by the printer.
Have the system administrator make sure the printer address is correct.
024 SERIAL LINE PARITY ERROR
VERIFY CONFIGURATION
1. The printed output may contain random ? (question mark) characters. Make a
configuration printout. Verify that the printer matches host serial configuration
settings for Data Protocol, Baud Rate, Data Bits, Stop Bits, Parity, Data Terminal
Ready, and Request to Send.
Set printer serial interface parameters to match those of the host.
2. Send a print job to the printer.
If the message appears, replace the serial data cable.
3. Send a print job to the printer.
If the message appears, go to Communications Failures, page 133.
025 SERIAL FRAMING ERROR
VERIFY CONFIGURATION
1. The printed output may contain random ! (exclamation point) characters. Make a
configuration printout. Verify that the printer matches host configuration settings
78 Troubleshooting