Rockwell Automation 1771-QC , D17716.5.25 SER/B SERVO POS - Manual (Page 214)

Troubleshooting
Chapter 10
10Ć2
processor work area or starting less than 64 words before the user
program area.
If a hardware fault is detected at power up, both the processor
communication fault and expander communication fault indicators turn
on.
Expander communication fault (EXPANDER COMM FAULT) -
This red indicator is normally off. It turns on to indicates a
communication fault controller between the 1771-ES and the 1771-ES
expander.
If a hardware fault is detected at power up, both the processor
communication fault and expander communication fault indicators turn
on.
Active - This green indicator is normally on. It turns off to indicate a
hardware fault on a 1771-ES expander. The active indicator blinks to
indicate one of the following improper module configurations:
The I/O chassis contains no 1771-ES expander.
The I/O chassis contains two 1771-ES expanders with the same
switch settings for axis identification.
The I/O chassis contains a 1771-ES expander with switches set for
axis 2, but no 1771-ES expander for axis 1. (If the I/O chassis
contains only one 1771-ES expander, it must be set for axis 1.)
The I/O chassis contains a 1771-ES expander with switches set for
axis 3, but no 1771-ES expander for axis 2.
The I/O chassis contains more than one 1771-M3 controller.
The I/O chassis contains another master/slave module combination
in addition to the servo positioning assembly. Master/slave
combinations include the Analog Input Module (cat. no. 1771-IF),
the Analog Output Module (cat. no. 1771-OF), the Stepper
Controller Module (cat. no. 1771-M1), and the Thermocouple
Input Module (cat. no. 1771-IX), and their respective slave
modules.
When the system is powered up, the three servo controller indicators all
flash on then off. If the processor is in the run mode with no fault, the
active indicator comes back on. If the processor is in the program or test
mode with no fault, the indicators all turn off and stay off until the
processor is taken out of the test or program mode.