Brother LX-200 Service Manual page 118

Switch Scan Circuit
This circuit in the main CPU scans the status of the Power switch, Cut button, Feed
button, Start button, and TRI switch (leaf switch) at 14 ms intervals to continuously
detect the status of each switch.
The circuit comprises a matrix of two output ports (P36, P37) and four input ports
(P40 to P43). A Low signal is output at 7 ms intervals from one of the two output
ports and the switch status at that time is detected from the status of P40 to P43).
When the main CPU detects that the Power switch was pressed, it turns the
power ON if it was previously OFF, or it turns the power OFF if it was previously
ON.
When the main CPU detects that the Feed button was pressed, it starts the
document and film feed operation. The document and tape are fed in
approximately 0.5 mm intervals but the document and tape are fed continuously
while the Feed button is held down.
When the main CPU detects that the Cut button was pressed, it operates the X-
cutter to start the film-cutting operation.
When the main CPU detects that the TRI switch was pressed, it starts the
trimming operation.
When the main CPU detects that the Start button was pressed, it starts feeding
and compressing the document in the selected automatic cutting mode.
Fig. 5.4-1 Switch Scan Circuit
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