Casio UP-250, Technical Manual

Page: 55 / 165

RAM (CPU internal 2K bit)
RAM is used as temporary storage for the following:
❏
Data received from the interface (receive buffer)
❏
Pattern data to be printed by the print head (printer buffer)
❏
Data used by the CPU (U5) during processing (flags, pointers, etc.).
Operation panel
The operation panel is located on the main circuit board and has 3 LEDs ( POWER , ERROR , and
PAPER OUT) and 1 switch ( FEED ). The POWER LED is driven at the same time as +5 V is
supplied by the power supply circuit. The ERROR and PAPER OUT LEDs are driven by U5.
Switch detection is also executed by the U5.
Various detector circuits
When the printer detects paper, the paper detector at the paper inlet turns the input signal to the
CPU (U5) LOW. This detector also functions as the semi-automatic loading detector.
A home position sensor is provided to detect the print head position. The input signal to the
CPU (U5) becomes LOW when home position is detected.
Figure 2-21 Operation panel circuit
P82
C17
R55
Q35 Q36
R56
R41
R54
R15
SW2
1 1 1
2 2 2
(PAPER)
D12 (ERROR)
D11 (POWER)
D13
+5V
U5
32 PF SW
1 ELED/DSW9
80 PLED/DSW0
P57/T03
P56/INT3/TI2
GND
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