REV.-A
Table 2-5. Functions of the Main
IC and Circuits
IC
or Circuit Location
Functions
TMP90C041
2C
Receives data from the host computer and loads the data to the input buffer in
RAM (under interrupt processing control). Expands the input data held in the
buffer to create image data. Loads this image data to the image buffer in RAM.
Transfers the image data to the
printhead
drive circuit. Also controls various parts
of the printer mechanism, such as the motors.
E05A49
4B
This gate array consists of seventeen components configured on a single chip:
Memory Management Unit
Wait Control Unit
Refresh Control Unit
Program ROM Select Unit
Centronics I/F Control Unit
Option Control Unit
Panel Control Unit
EEPROM Control Unit
General Output Unit
HPW
Differential Unit
HPW
Pulse Limit Unit
Bit
marf{pulation unit
Head Control Unit
Internal Clock Generate Unit
Internal
1/0
and MMIO Decode Unit
Output Data Multiplex and Input Data Latch Unit
PU41 35
IC8-IC 13
This is a drive circuit for the
printhead.
h consists of six chips.
PROM
3A
The PROM contains the program that runs the
CPU.
RAM 4A
The RAM contains the CPU working area and the various buffers. (5A is not used
5A
and not installed in the 80-column printer.)
MROM 1A
The mask ROM contains the character design (also called the character
(Mask ROM) 2A generator).
EEPROM 5C
The
EEPROM is an electronically
writable
and erasable ROM that contains infor-
mation such as the top-of-form position.
Vref Circuit
IC
This circuit generates the reference voltage used in the A/D converter in the CPU.
TL431
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