Interprocessor Communication (IPC)
RTHC-SVD01B-EN 63
12-4. Procedure for Troubleshooting IPC
Communication Diagnostics
12-4 a. Communication Diagnostics
1. Place the UCP2 in “Stop” by pressing the stop key once. Record
the active IPC diagnostics as shown in the Diagnostics Report of
the CLD. The communication failure diagnostics and their mean-
ings are shown in IPC Diagnostics of the RTHC-IOM manual.
2. Check the IPC connections to all modules. Make sure the twisted
pair wires that plug into each modules' J1 connector are making
good contact with the wire. Be sure each connector is not clamp-
ing down on the wire insulation.
3. Determine which modules are not talking. These modules must
be affected by one of the previously stated problems. If the 1U1
is reporting that it cannot talk to any of the other modules. Sus-
pect a bad 1U1. If the there is a comm loss involving the 1U2,
1U5, and 1U6, suspect a wiring problem early in the daisy chain
link. If only one module is not talking, suspect a loss of power.
Refer to figure 12-1 for IPC daisy chain wiring.
4. Determine which modules are still talking. Wiring to these is likely
to be OK.
5. Try disconnecting the link or jumping out modules in the link at
various places. Reset the diagnostics and note which diagnostics
reappear.
The 1U7, 1U2 and 1U3 are connected directly to the 1U1 and are
not part of a daisy chain.
6. Verify that the polarity of the IPC link is correct.
7. Using a voltmeter set to AC volts, measure the voltage at the J2
connector on each module. It should read between 20 and 28
VAC. Also check the green connector to make sure it is securely
plugged into the module. Inspect each screw terminal to be sure
they are not clamping down on the wire insulation.
8. Most of the UCP2 modules have 24 VDC and 5 VDC test points
on the board. They are clearly labeled and accessible without
removing the sheet metal covers.
9. Using a voltmeter set to DC volts, measure the 5 volt test point. It
should be between 4.75 VDC and 5.25 VDC. Measure the 24 volt
test point. It should be between 23 VDC and 25 VDC. If any of the
voltage measurements are not within the acceptable range,
replace the module.
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