User manual

95.08.23.11.29

Color LaserWriter 12/600 PS Basics & Theory 1–36

Between-

Pages APC

Immediately after the initial APC, the printer performs the between-

pages APC for pages and colors. The CPU sets the

/VDOENB signal to

“H” during the unblanking period.

Note: In order to detect the

/BDI signal, the laser diode is turned on

even during the period that it does not scan the laser beam across the

drum. This is referred to as the “unblanking period.”

This causes the laser diode to emit the laser beam at the intensity set

during the initial APC. To ensure that the

PDIN signal is at the speciﬁed

value, the

APCLW signal (8-bit) is changed to correct the LLCNT signal

so as to compensate for the offset from the target value.

Horizontal

Sync Control

A small beam-detect (BD) mirror is ﬁxed in the optical path of the laser

beam. Upon reaching the scanning start position, the laser beam is

reﬂected by the BD mirror to the BD board in the laser/scanner

assembly during the unblanking period. On receiving the laser beam,

the BD board generates the beam detect input signal (

/BDI) and then

sends it to the gate array in the DC controller board. The gate array

produces the horizontal sync signal (

LSYNC) based on the /BDI signal

and then sends it to the I/O controller.