Epson Stylus Color 440, Service Manual

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EPSON Stylus Color 440/640/740 Revision A
Chapter 2 Operating Principles 72
2.2.4.5 DRAM Control
In the Dynamic RAM control, output and formation of CAS and RAS
control signals become necessary in addition to the output of CS signal.
The CPU not only controls that but also perform the output of CS signal
of P-ROM. Refresh timing is performed in the CAS Before RAS.
2.2.4.6 Print Head Control Circuit
The print head control circuit of Stylus Color 440/640/740 has following
characteristics.
Common wave form circuit became one HIC.
Slight vibration mode is added.(when the CR motor is
accelerating)
High speed drive 14.4Khz (trapezoidal wave form
Big Nozzle configuration (resolution in the vertical
direction)90dpi
(However, black nozzle is 2 lines structure)
Also, Stylus Color 440/640/740 does not have Micro-dot control as dot
shooting control, but there are two types; Normal-dot and Normal dot-
2dot.Normal-dot-2dot was called Dual Firing in the Stylus Color IIs/820.
These setting/change are controlled automatically by setting of the
printer driver that is determined by the user. The followings are required
conditions to perform the normal-dot 2-dot.
At the OHP, Normal sheet setting (360X360 dpi)
At the ordinary paper and resolution 360X360 dpi setting
The control circuit is considered as 2 divided parts; 1) trapezoidal wave
form generation circuit (common drive circuit) to drive PZT in the head,
and 2) Nozzle-selector drive circuit to determine which nozzle should be
used. The Nozzle-Selector is attached to the head unit just like the
previous models. The common drive circuit is hybridized as one HIC
and mounted on the main control board.
See the following pages for the head drive circuit block diagrams for
each printer.