122 Pamux User’s Guide
GENERAL TROUBLESHOOTING
1. It is a good idea to disable the watchdog timer while troubleshooting. On B4 and B5 boards,
install jumpers 5 and 6 to do so. On B6 boards, install jumper 8 to disable the watchdog.
2. Apply power to the Pamux unit to be tested. If the power LED doesn’t light, check the fuse on
the mounting rack. Note that the power LED may be on the brain board or on the mounting
rack.
3. Run a small program to continuously read one Pamux board. (The Opto 22 BBS includes utilities
that will do this; search for PMXSCAN.ZIP or PAMSCN.EXE.) While communicating, does the
watchdog LED go out? If not, check the AC28’s base address jumpers. Does the respective
address LED blink? If not, check the address jumpers on the Pamux board.
4. If a B4 or B5 board reads inputs properly but does not write outputs correctly, check the board’s
reset level (jumper 7).
5. The Pamux driver (used in PMXSCAN.EXE and PAMSCA.ZIP) will return an error code of -7 if
the driver cannot gain access to a B6. Should this occur while testing, check the B6 board’s 5V
power, check its reset level (jumper 7), and make sure the terminator board is inserted and
properly attached to 5V.
6. On the B6 board, if communication is working correctly but the board does not read proper
values, check the ±15 VDC power. Remember that the ±15 VDC power supplies must be within
±0.25 VDC.
NOTES ON LEDS
1. The address LED on the B4, B5, and B6 boards will blink on when the board decodes a match
between the address lines on the Pamux bus (see “Bus Pin Definition” in Chapter 4) and the
address jumpers on the board. The state of the reset line has no effect on the address LED.
2. The watchdog LED on the B4 and B5 boards will stay on as long as no communication is taking
place (the read and write lines on the Pamux bus are not strobing). Once the read or write line
strobes, the watchdog LED will go off. If no other communication takes place, the watchdog
LED will stay off for approximately 1.6 seconds and then turn back on. If the read or write line
strobes before 1.6 seconds has elapsed, the watchdog LED will remain off for at least another
1.6 seconds. As long as the system is reading or writing faster than once every 1.6 seconds,
the watchdog LED will remain off. The state of the reset line has no effect on the watchdog
LED.
3. The access LED on the B6 brain board will light when the host device has access to the dual-
port RAM and the B6 processor wants access. (See “Reading from and Writing to Analog
Pamux Stations” in Chapter 4.)
TROUBLESHOOTING AND TIPS
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