User manual

95.08.23.11.29

Color LaserWriter 12/600 PS Basics & Theory 1–37

Laser Diode

Emission

Control

The laser driver circuit turns the laser diode on or off in accordance

with the laser drive signal received from the PWM-IC when the video-

enable signal (

/VDOENB) is “L” and the forcible laser-on signal (/LSON)

supplied by the DC controller is “H.” The gate array (IC109) applies

left/right and top/bottom margin masking to the video signals (

VDO7-

VDO0) in accordance with the paper size data sent by the I/O controller,

and then sends them as

DV2-DV9 signals to the PWM-IC in the

laser/scanner assembly. The paper size data is supplied to the CPU by

the cassette-size sensing switch for cassette paper feed or by the paper

size speciﬁcation command issued by the I/O controller for manual

paper feed.

Notes:

1 The shaded area permits writing with the laser beam.

2 Times T1 and T2 vary depending on the paper size.

3 If no paper size is speciﬁed by the paper size speciﬁcation command

from the I/O controller for manual feed, the printer does not recog-

nize the paper width. So the T1 and T2 values are assumed to be

legal size, the maximum paper width for the printer. The CPU deter-

mines the actual paper size from the paper length detected by the

paper leading-edge sensor (PS303) when the leading edge of the

paper has passed through PS303. Subsequently, the image is

masked based on the detected paper size.

8 mm

/TOP

Top/Bottom Margin

Masking Signal

2 mm

2 mm 2 mm

/LSYNC

Left/Right Margin

Masking Signal