7. C300 Controller Operation 
7.1. C300 Controller start up 
Series 8 C300 Controller User's Guide 
Honeywell 
redundant controller, the controller enters the No Database 'NODB' execution 
state.  If the controller's database has been retained, the execution state is 
'IDLE.' 
 
Secondary controller first displays '????' until its redundancy role is 
determined. Once determined the secondary controller indicates it is an 
unsynchronized secondary or synchronized secondary. The secondary 
controller also shows the controller's execution state, which is 'BKUP.' 
 
Figure 5 describes the C300 Controller startup routine and the possible controller states 
when the controller is in the Boot mode. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 5 C300 Controller Startup and Boot Mode indications 
C300 Controller states in boot mode 
At the conclusion of POST, the C300 determines if there is a valid Application Image 
present in the controller and if it should then transition to executing this Application 
image (Application mode) or to continue in the Boot mode.