Reset Circuit - Epson DLQ-3000 Service Manual

Operating Principles

2.3.2 Reset Circuit

The hardware reset circuit for this printer has 2 reset ICs: RST592D (IC22) and RST594E
(IC20). When the +5 v for logic line is unstable dew to power-on, it outputs the reset signal
until the +5 VDC line is stabilized to avoid abnormal operation of the printer. RST592D
monitors the Flash-ROM with the threshold voltage set at approximately 4.2 VDC. It outputs
the reset signal until the +5 VDC line is stabilized to 4.2 VDC. The Flash-ROM recovers
from the reset condition before the CPU and the gate arrays recover from the reset
condition. RST594E monitors the CPU and the gate arrays. The threshold voltage is set at
approximately 4.2 VDC. The reset signals is kept output until the +5 VDC line is 4.2 VDC.
Since the reset signal from the RST592D is sent to the manual reset terminal (MRST) in the
RST594E via the output port of the CPU, the Flash-ROM recovers from the reset condition
before the CPU and the gate arrays recover from the reset condition.
Figure 2-13. Reset Circuit Block Diagram
2-19
Rev. A