Revision 6    HC900 Process & Safety Controller User and Installation Manual  177 
21 April 2017 
Lead and/or Reserve Controller 
Action(s) 
HCDesigner/HC 
Utilities Indication 
There are slave blocks 
in the configuration, 
and no communication 
port is configured as a 
Modbus master. 
  MSTRFAIL pins on ASYS and 
FSYS blocks turn on. 
  All Modbus slave and Modbus 
read blocks freeze their output 
pins to the last value. 
  All slave blocks have their BAD 
COMM pin on. 
  All slave blocks have their NO 
SCAN pin on. 
  IN SCAN STATUS is set to NO 
for all slaves. 
  COMM STATUS is set to BAD 
for all slaves in the function block 
diagram. 
  Statistical counters for all slaves 
are 0. 
1. Use the OI, HCDesigner, or 
HCUtilities to configure one of the 
serial ports (S1 or S2) as a master. 
2. Use the OI, HCDesigner, or 
HCUtilities to download a 
configuration that has no slave 
blocks. 
Controller mode is 
changed to RUN-
Locked while there are 
forces present on 
safety worksheet. 
  Controller will not go to RUN-
Locked mode. 
1.  Change mode back to RUN 
mode OR 
2. Clear all safety forces using HCD 
through Monitor->Forced 
Blocks OR 
3.   Force a cold-start 
In HCD, "System 
Diagnostics" 
shows status as 
"Invalid Change of 
Mode" 
Controller mode is 
changed to RUN-
Locked when safety 
configuration is 
changed at run-time. 
  Controller will not go to RUN-
Locked mode. 
7.  To clear the diagnostic: 
8.  1. Change mode back to RUN 
mode OR 
2. Force a cold-start 
In HCD, "System 
Diagnostics" 
shows status as 
"Safety 
Configuration mis 
match" 
One of the following 
microprocessor 
exceptions occurred: 
  Watchdog timer 
timeout  
  Address error 
  Prefetch error 
  Data abort error 
  Software interrupt 
  Undefined 
instruction error 
At the time of the exception, the 
microprocessor resets. If it’s the 
Lead controller, and there is an 
available reserve, a failover occurs.  
When the microprocessor 
completes its reset condition, it will 
become an available reserve if a 
lead is present or become a lead if 
no lead is present.  
This diagnostic will cause the 
HWOK pins of the AYSY and FSYS 
blocks to be turned off. 
To clear the diagnostic, force a cold 
start.  
If the problem reoccurs, try the 
following: 
1. Ensure the system is properly 
grounded 
2. Ensure the system is properly 
isolated from external noise sources 
3. Upgrade the firmware 
4. Replace the CPU board. 
5. Contact Honeywell Personnel. 
If the lead’s status 
LED is indicating 
the failure, see 
CPU in the “Lead 
CPU Diagnostics” 
display. 
If the reserve’s 
status LED is 
indicating the 
failure, see CPU in 
the “Reserve CPU 
Diagnostics” 
display.   
If the lead’s status 
LED is indicating 
the failure, see 
CPU Diagnostics 
in the “Lead 
Diagnostics 
Overview” dialog 
box. 
If the reserve’s 
status LED is 
indicating the 
failure, see CPU 
Diagnostics in 
the “Reserve 
Diagnostics 
Overview” dialog 
box. 
One of the exception 
vectors located in RAM 
became corrupted. 
The exception vector was 
automatically corrected in the 
controller’s RAM and the controller 
continues to operate normally. 
This diagnostic will cause the 
HWOK pins of the AYSY and FSYS 
blocks to be turned off.