Rockwell Automation 1785-Vx0B, D17856.5.9 PLC-5 VME VMEbus Programmable Controllers User Manual - Manual (Page 250)

D Appendix
D-1
Troubleshooting
Read this appendix when you troubleshoot the PLC-5/VME processor. For
the PLC-5/VME processor to maintain integrity of the ladder program and
data files, the VME power supply must assert ACFAIL at least 9 ms in
advance of the +5 VDC supply dropping beneath 4.75V. If power is
removed and re-applied to the VME system and the PLC-5/VME powers
up faulted after previously having a good program in it, it may be the result
of not having ACFAIL properly asserted on the VME backplane.
The VMEbus contains several daisy-chained control signals. Almost all
VMEbus backplanes contain jumpers for these control signals to allow
systems to operate with empty slots. Failing to install these jumpers
properly is a common source of problems in configuring a new
VMEbus system.
See Chapter 2 for detailed information on setting these jumpers.
The LEDs on the front panel have the following meaning:
When you see
this light on: It means that:
Battery low The battery output is weak; the battery needs to be replaced.
Proc run/fault If green, the processor is in run mode and has not faulted.
If red, the processor has faulted.
Force Continuous on denotes forces enabled.
Blinking denotes forces present but not enabled.
Ch0 status Data is being transmitted or received on channel 0.
SYSFAIL The processor is driving the VMEbus SYSFAIL signal.
Master access The processor is performing a VMEbus access.
Slave access Another VMEbus master is performing an access to the processor.
Appendix Objectives
VME Backplane Jumpers
VME LEDs