Watlow Electric Revision 5 - Manual (Page 70)

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If the green light is on, then the orange light light is a communications
indicator. The orange light will appear whenever the PIOM has decoded a
communication containing the address of the PIOM as set in the DIP switch.
Thus the conditions for establishing the orange light in the presence of the
green light are:
1) PIOM working.
2) Host and PIOM set at the same BAUD rate.
3) PIOM address switches set correctly.
4) Host sending out proper communication containing correct
address.
No other conditions are guaranteed to exist. For instance, this does not
guarantee proper communication error checking protocols.
If the green light and orange light are both on, first check error protocol as
set by the DIP switch and by Anasoft, then check the communication
wiring. If the green light comes on but the orange light does not, then check
the above in addition to checking the PIOM address switch and the BAUD
rate.
11.4.2 Process Ready Light is Off
If on applying power to the controller, the GREEN READY light is not
illuminated on the processor board mounting panel:
Use a voltmeter to measure the 5 VDC supply to the controller backplane to
make sure that the voltage measures between 4.9 and 5.3 volts D.C. A low
voltage detect circuit on the processor board will prevent operation if the
supply voltage drops below 4.75 volts D.C. (+/- .1 volt).
If there is non power or a low supply check the AC input power, and the
power supply output at the power supply terminals.
If power is present at the proper voltage contact ANAFAZE as the probable
cause is PROCESSOR I/O MODULE problem.
11.4.3 Orange Communication Light Remains Off
Normally this will also cause a COMMUNICATION ERROR message
when running Anasoft. If this occurs and the Green Light is on:
Verify that the communications options specified in the Anasoft Installation
program (QINSTALL) match those specified by the option bit switch
settings on the processor board. These options include the baud rate and the
method of error checking to be used.
Verify that the controller address bit switch settings on the processor board
are correct. If you have only one controller in your communications circuit
it's address should be 0 (all address bit switches off).