Detecting The Paper Size - Canon LBP-2000 Service Manual

B . Detecting the Paper Size
1 . Detecting the size of paper in the cassette
When the cassette is set in the Printer, specific switches are turned on: combinations of the states
of the following switches are used by the CPU to detect the size of paper inside the cassette or the
presence/absence of the cassette:
Paper size
A3
A4R
A4
A5
B 4
B 5
11 x 17
LGL
LTR
EXEC
No cassette
To prevent a mistake in the selection of a paper size by the user, the Printer is designed to measure
the time between when the registration paper sensor (PI101) detects the leading edge of paper and
when the trailing edge of the paper leaves it. If the measurement does not correspond to the paper
size found based on a combination of the states of the switches indicated in the table or if it is
different from the length selected by the video controller for the paper placed in the multifeeder
tray by ±10 mm, the CPU will identify a size mismatch condition and communicate the fact to the
video controller.
2 . Detecting the size of the paper in the multifeeder tray
As in the case of the cassette, the multifeeder tray uses the registration paper sensor (PI101) to
find out the size of paper. However, a mismatch in size cannon be detected for A4R (vertical)/LTR-
R (vertical) or B5/Executive-R (vertical) because of limited paper length.
When Universal is selected for the size, detection for a mismatch in size will not be executed.
Table 2-5-1
Paper size detecting switch
P S S N 4 P S S N 3
(leftmost) (middle left)
O N O F F
O F F O F F
O F F O F F
O F F O N
O F F O N
O N O N
O F F O N
O N O F F
O N O N
O N O F F
Other than above
CHAPTER 2
P S S N 2 P S S N 1
(middle right) (rightmost)
O F F O F F
O N O N
O F F O N
O N O N
O N O F F
O F F O F F
O F F O N
O N O N
O F F O N
O N O F F
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