COPYRIGHT © 1999 CANON INC. CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)E. Controlling the Laser Diode EmissionThe laser drive circuit turns on and off the laser diode according to laser drive signalsfrom the PWM IC when the image enable signal (LENB*) from the DC controller PCB is‘0’ and the APC sampling timing signal (SAMPLE*) is ‘1’.The GA (IC204) puts video signals (DVDO0 through 7*) through masking processingfor left/right and top/down directions for transmission to the PWM IC.The paper size is communicated to the D-CPU (IC201) by means of a paper sizecommand coming from the cassette size detecting switch in the case of cassette pickupor from the printer board*1 in the case of multifeeder pickup.Figure 3-202Note:1. The laser beam is capable of writing within the shaded area.2. T1 throng T3 differ according to paper size.3. If the paper size command from the printer board does not indicate a paper sizewhen the multifeeder is used, the printer unit assumes T3 is 12x18.5 (maximumpaper size) in the absence of data.The multifeeder tray is equipped with a paper width sensor (PS1701) for detectionof the width of paper.The CPU identifies the size of paper in relation to the length of print paper detect-ed by PS1 when the trailing edge of the paper moves past the registration papersensor (PS1).*1 Reader controller PCB (when making prints with the reader unit installed).CHAPTER 3 LASER EXPOSURE SYSTEM3-8T25 mm5 mm 5 mmT1TOPR*5mmHORZENVERTENTop/bottommasking signalT3LSYNC*Left/rightmasking signalDownload free service manual at http://printer1.blogspot.com
