PRINCIPLES OF OPERATION
REV.-A
The control circuit consists mainly of the following ICs:
0 µPD7810HG CPU (5B)
The µPD7810HG executes the program in the PROM (6A) and controls all the printer operations. Upon receiv-
ing the RESET signal, the CPU begins executing the program from address 0000 hex.
. PROM (6A)
The PROM includes the control program (firmware).
0 HM65256 PSRAM (5A)
The HM65256 PSRAM is external memory for the CPU. It is used as an input data buffer and line buffer
for expanding data, and as working area for the program.
0 E01A05 Gate Array (7A)
The E01A05 functions are as follows:
1. Parallel I/F
2. Address decoder
3. Bank register
4. Data address multiplexer
5. Reset
6. CR motor control
0
E05A02 Gate Array (1 A)
The E05A02 was developed for 24pin, dot-matrix printers and is used to simplify the interface between the
CPU and the printhead.
0
EEPROM (7B)
The EEPROM has a 128-bit memory, which is used to store the paper position.
0 M10A17 or M10A20 Mask ROM (1M CG, 4A)
The M10A17 or M10A20 mask ROM incorporates the character generators. The ROM includes character
design.
Other control circuits are as follows:
0 Paper-Feed Motor Drive Circuit
This circuit drives the paper-feed motor, which is a four-phase, stepper motor. The CPU controls the motor’s
rotation (position and speed).
0 Carriage Motor Drive Circuit
The carriage motor drive circuit drives the carriage motor, which is a four-phase stepper motor. The rotation
of the motor (position and speed) is controlled by outputting the phase switching signal by the E01A05 gate
array.
2-12
LQ-510
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