Service manual

2-18 Mechanism Configuration and Operating Principles Rev. B
Confidential
CPU
The printer uses an external 8-bit and internal 16-bit CPU, with an external clock of 14.7 MHz.
The CPU (U5) controls the internal processing of the printer according to the printer control
program written in EPROM (U8).
CPU pin functions
Pin
No.
CPU
Function Signal Name I/O Level Description
1 P57 ELED/DSW9
I/O TTL ERROR LED. LOW: on. DIP SW 2-1 is read when
P100, P101 are LOW.
2 NMI NMI I TTL Not used (connected to +5 V directly).
3P100 AC1/DSEL
O TTL Auto cutter drive (1) and DIP SW read selection.
LOW: read (read once after initialization).
HIGH: break status when used as motor control
port.
4P101 AC 2/DSEL
O TTL Auto cutter drive (2) and DIP SW read selection.
LOW: read (read once after initialization).
HIGH: break status when used as motor control
port. This pin must change at the same time as
P100.
5 AVCC AVCC I (+5 V) Analog/digital converter standard voltage.
6 AVSS AVSS I (0 V) Analog/digital converter GND terminal.
7 P60/AN0 V DTC I Analog +24 V power voltage detection.
8 P61/AN1 HD TEMP I Analog Head temperature detection.
9 P62 NE I TTL Paper roll near-end detection.
LOW: no paper; HIGH: paper present.
10 P63 DK S I TTL Drawer open/closed. LOW: open.
11 P64 RE I TTL Paper roll end detection.
LOW: paper present; HIGH: no paper.
12 P65 HP DTC I TTL Carriage home position sensor.
LOW: home position.
13 P66 DET I TTL Host interface DET.
14 P67 AC RST I TTL Auto cutter position detection (reset).
15 VCC VCC I (+5 V) Main power terminal.
16 P70 CTS
I TTL Host interface CTS. LOW: on.
17 P71 CCE
O TTL 4M ROM CE signal. LOW: active.
18 P72/RXD1 RD
I TTL Host interface RD. LOW: on.
19 P73/CLK1 CLK IN/DTR I/O TTL Host interface CLK IN/DTR.
20 P74/TXD1 SD
O TTL Host interface SD. LOW: on.
21 RESET
RESET I --- CPU reset input. LOW: on.
22 CLK CLK O TTL Not used. Open.
23 VSS VSS I (0 V) GND terminal.
24 X1 X1 I --- Connected to ceramic vibration generator.
f=14.74 MHz ± 0.5%.