Canon FACSIMILE BASIC 2000 Service Manual page 106

RECORDING SECTION
4.4.1 Main video interface signals
• nRDY signal (Ready)
This signal is issued by the printer engine control section to the video con-
trol section to show that it can start or continue printing.
• nPRNT signal (Print)
This signal is issued by the video control section to the printer engine con-
trol section to instruct start or continuation of printing. The video control
section sends this signal when one full page worth of data is present and
the nRDY signal state is "Low." When the printer engine control section
receives this signal, it prepares the printer for printing by rotating the pho-
tosensitive drum and picking up the recording paper, for example.
• nTOP signal (Top Of Page)
This is the vertical scanning (vertical direction) sync signal for the LASER
beam, and is used for printing the start of the image (first line) at an appro-
priate position on the recording paper.
4–28
Printer engine
Video
control section
control
section
nRDY Ready signal
nPRNT Print signal
Vertical sync signal
nTOP
nBD Horizontal sync signal
nVDO Video signal
(image data)
nRDY
nPRNT
nTOP
nBD
nVDO
Fig. 4-29 Video Interface Signals
LASER drive
signals
Fixed period
of time
1 line's worth of data
LASER/scanner
section
H
L