WILLETT 430, Service Manual

Page: 74 / 207

Technical Description: Control Electronics
Issue 2
57
Part No. 306-0430-102
Major Components
The CPU board Figure 23 ( 1 ) contains the hardware and software for system control. It comprises the following
major components:
•
The CPU board ( 1 ) is a multi-layered motherboard that monitors and controls all of the major printer
functions. The board interfaces with the I/O board, PSU module, expansion board (if fitted) and external
devices (if connected) to provide an integrated product coding system.
•
Integrated Circuit (IC) U31 (
2
) produces keyboard drive signals to determine which key has been pressed.
•
IC U40 and IC U41 ( 3 ) are flash memory devices and are programmed by Willett to hold the following
information:
application software.
printer default setup.
•
IC U38 and IC U39 ( 4 ) are two integrated circuit Random Access Memory (RAM) devices that contain the
printer configuration, calibration and message storage memory. To avoid loss of data when the printer is
switched off they are backed up by a Nickel Metal Hydride (Ni-MH) battery.
•
IC U19 (
5
) is the microprocessor that monitors incoming data from the I/O ports and translates software
commands into machine statements that control the electronic system and ink system to produce a printed
message.
•
IC U21 ( 7 ) is a Real Time Clock (RTC) which contains a clock/calendar. It has a battery backup so that the
current time and date do not have to be manually set each time the printer is switched on.
•
The Ni-MH battery ( 6 ) supplies the voltage necessary to retain Real Time Clock (RTC) and RAM data when
the printer is switched OFF. The battery is automatically charged when the printer is switched ON.
•
IC U9 ( 8 ) is a Dual Universal Asynchronous Receive Transmit (DUART) which can be configured to
interface with different devices to transmit and receive data.Connectors