Epson Stylus Color 640 Service Manual page 65

EPSON Stylus Color 440/640/740
[CPU]
The 16-bit CPU which is mounted on Stylus Color 740 is running at
24Mhz. Gate array manages most of controls and monitors. Likewise
the Stylus Color, the D-RAM is applied for RAM which is used as work
area for receiving data and developing the data and CPU manages its
control such as CE, RAS/CAS controls.
[Gate Array]
E05B588 controls following functions.


Motor control
Each motor performs data transmission that motives Micro-Step.


Head voltage control
In the ink jet printers, drive voltage wave form (trapezoidal wave
form) in order to drive PZT is formed in the various shapes
according to the types of the printers. Therefore, it is necessary to
form appropriate drive form for each head. Head voltage control
forms necessary wave form for each control signals and outputs
them.


EEPROM control
The correction value to eliminate the error of each printers at
production process is installed in the fixed address of IC. When the
power is turned off, the contents set by users is written instantly, and
is red to the RAM when the power is turned on.


Sensor Data
The sensor detects information at the various conditions, which is
necessary for the printer operation. The gate array recognizes
signals and changes over to the next control.
Chapter 2 Operating Principles


Timer Data
The timer IC that uses lithium battery as power source monitors how
long the power is off. When the power is turned on, it is changed to
appropriate cleaning level according to the time that the power is off.


Serial I/F Control
The gate array receives serial data through the transceiver IC.


Parallel I/F control
With the use of IEEE1284 Nibble mode, it became possible not only
to receive the data from the host but also to return various
information which the printer possesses to the host.


USB I/F Control
The transceiver circuit which control the USB interface has been
incorporated into this gate array.
[Common Driver IC]
The trapezoidal wave form circuit for head drive is became to HIC from
the previous discrete structure. Because of this, it is not necessary to
adjust the adjustable VR on the board during production process.
Various electric charge/discharge control signals are all processed in
the HIC.
[CR/PF Motor Drive Circuit]
Constant current drive is performed by the HIC. Out of this, only CR
Motor is controlled for Micro-Step control and HIC becomes possible to
flow the appropriate current value at each steps. (PF Motor has only 1-
2, 2-2 phase drive method). Also, bipolar drive is performed on the 4
cables individually.
Revision A
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