Canon LBP-1120 Service Manual page 41

CHAPTER 2
The CPU detects the following failures and error by monitoring /BDI signal sent from the BD sensor, and reports it
to the interface controller:
1) Scanner Failure
When the /BDI cycle does not reach the specified value within 3.5 seconds after the scanner motor was forcibly
accelerated at its start-up.
2) BD failure
When the /BDI signal is not detected within 0.1 seconds after the scanner motor was forcibly accelerated. Or, the
scanner became ready once and then the /BDI cycle is not detected in the specified value for 2 continuous seconds.
3) BD error
When the /BDI signal is not detected in the specified cycle while the engine controller is outputting the /BD signal
to the interface controller.
The CPU does not report the BD error to the interface controller, if it detects a door open within 0.2 seconds after
detecting a BD error.
Also, the CPU cancels the BD error, if it detects a scanner failure or BD failure after detecting the BD error.
2 - 22