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PK-232 TECHNICAL MANUAL
7.4.
Terminal Interface Troubleshooting
If the controller does not appear to start, respond to commands or accept data from the ter-
minal or computer, the problem may be in the RS-232 interface. The following troubleshoot-
ing suggestions can aid in resolving problems related to the RS-232C port.
7.4.1.
Symptom: Controller does not communicate with the terminal
Use a 'breakout box' or oscilloscope to verify that correct control voltages are present on
pin 4, 5, 6, 8 and 20 of J2, the RS-232 I/O connector.
o
Verify that the DTR line on Pin 2 of J2, the RS-232 I/O connector is not being held
low.
If the controller software flow control is disabled by setting START, STOP, XON and XOFF
to $00 and XFLOW to OFF, the controller will not send data to the terminal unless its DTR
is asserted.
If th computer or terminal does not provide the DTR/CTS protocol or "handshake", the
DTR/CTS lines (pins 20 and 5 on J2) should not be connected.
o
Verify that the voltages on the controller are correct.
If the tests are valid, verify the signal on U7 pin 27 with an oscilloscope.
o
Recycle the power switch on the controller. Transitions on this pin shortly after reset
indicate that the controller is sending data.
o
Verify that transitions are also present on U10 pin 1.
7.4.2.
Symptom: Controller signs on with mutilated data
If the terminal displays strange characters, 'garbage', graphics, etc., one or more of the
following parameter values is incorrectly set and does not agree between the terminal and
the controller:
o
Set the terminal 1200 bauds if possible, seven data bits, even parity, and one stop
bit. These are the default settings stored in EPROM.
o
Restart the controller by cycling the power switch OFF then ON (out then in). The
sign on message should appear.
If the controller still prints gibberish:
o
Verify that the terminal is set to 1200 bauds and recycle the power switches on both
the controller and terminal.
If the sign-on message still fails to appear:
o
Verify signals with an oscilloscope connected to TXD pin 25 of U7, the Z8530 chip,
and then at the X32 baud rate clock (38.4 kHz at 1200 bauds) on pin 14 of U7.
PK232TM Rev. A 5/87
data rate (TBAUD)
data word length (AWLEN)
parity (PARITY)
number of start and stop bits
7-5
CHAPTER 7 – TROUBLESHOOTING
Page 44
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Table of Contents
Troubleshooting
