Timer Circuit; Dram Control - Epson 440 Service Manual

EPSON Stylus Color 600
2.2.2.4

Timer Circuit

The lithium battery is mounted on the C200 main board and calculates how long the printer is not in used.
The timer IC(IC10) starts counting with oscillation motivated by the CR3 using this battery as a power
source. The figure below shows connection of the Timer circuit.
The followings explain about operation of this circuit.

When the printer is on, power is supplied to the Timer IC by applying +5V quickly through
the D4.

This power is also used for the power to oscillate the outer CR3. The oscillation wave form is
input to XIN terminal.

Since the oscillation wave form of CR1 is analog waveform, it is processed into the
pulse form in the Timer IC.

When the printer is turned on, the Timer IC outputs power off time as serial data to the gate
array.

Once the printer is turned off, 3VDC of BAT1(lithium battery) is supplied as power source for
the Timer IC through D1.

Since +5V at the power on is higher than +3V of the lithium battery, the power is not being
consumed from the lithium battery.
2.2.2.5

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 TMP95C061AF not only controls that but also perform
the output of CS signal of P-ROM. Refresh timing is performed in the CAS Before RAS.
2-26
Figure 2-23. Timer Circuit Block Diagram
Rev. A