Canon CLBR 460ps Service Manual page 99

4. Laser diode emission control
The /VDO signal input to the DC controller from the video controller is performed mask pro-
cessing in the gate array (IC1003) and sent to the PWM IC as the LASER DRIVE signals (VOUT0
to 7). The gate array performs horizontal and vertical mask processing to the VDO signals
according to the paper size data. The paper size data is supplied to the D-CPU by the paper size
detection switch when the paper pick-up source is the cassette and by the paper size specifica-
tion command sent from the video controller when it is the multi-purpose tray.
The laser drive circuit turns ON/OFF the laser diode according to the LASER DRIVE signal
(/VDATA) output from the PWM IC when the LASER EMISSION ENABLE signal (/LSENB) and
LASER FORCED EMISSION signal (LON) are "L."
/LSYNC
HORZEN
Notes: 1. The shaded area is where the laser beam is permitted to write.
2. Times T1 to T3 vary according to the paper size.
3. When the paper pick-up source is the multi-purpose tray, the paper width cannot be
determined if no paper size specification command is sent from the video controller.
In this case, the value of T1 to T3 are set to be that of Letter size (default paper size
of the multi-purpose tray).
Left/right
margin
masking
T1
signal
2 mm
Figure 2-3-3
T2
2 mm
CHAPTER 2
2 - 41