Canon CP660 Service Manual page 80

CHAPTER 3 LASER EXPOSURE SYSTEM
The speed is controlled based on the laser scanner motor speed signal (SCMFG)
from the laser scanner motor, while the phase is controlled using the BD signal. (See
Note.)
When the printer unit is turned on and the PRNT* signal is sent to the D-CPU (PC201)
on the DC controller PCB, the D-CPU sends the rough adjustment acceleration signal
(VUP*) to the speed control voltage generation circuit through the GA (IC204).
As a result, the motor drive voltage generation circuit generates the laser scanner
motor drive signal (SCND) to rotate the laser scanner motor. The laser scanner motor
feeds the SCMFG signal to the GA (feedback) to communicate its revolution, and the GA
controls the VUP8 signal and the VDWN8 signal until a specific revolution is reached.
When the laser scanner motor reaches a specific revolution, the GA switches from the
SCMFG signal to the BD* signal as the target of detection to start control of the laser
scanner motor (including phase control).
The GA adds the fine adjustment acceleration signal (PLUP*) and the fine adjustment
deceleration signal (PLDWN*) to the rough adjustment signal, and controls the fine
adjustment signal (PLUP*, PLDWN*) until the phases match based on the BD* signal
from the BD PCB, consequently causing the laser scanner motor to rotate at a specific
speed.
When a specific revolution is reached, the GA writes BDRDY to the internal register
to enable the D-CPU (IC201) to judge whether the laser scanner motor is rotating at a
specific speed by monitoring the data.
Note:
The printer unit deposits four color toners on a single sheet of paper, requiring that the
laser write start position be accurate. To ensure correct laser rotation (revolution), the
printer unit controls the motor including its phase.
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COPYRIGHT © 1999 CANON INC.
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CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)