1. Introduction GEM80-400
Page 1-6 ALSPA GEM80-400 CONTROLLER TECHNICAL MANUAL Issue 3 04/99
As a safety measure, two pairs of watchdog relays are fitted to the backplane. These
watchdogs open in the event of a detected controller failure. Refer to Chapter 11 of this
manual for further details.
1.4.1. Processor Module
The 8239 Processor Module is used to handle all I/O highway communication, serial
communication and to run the control program and the ladder compilation.
The processor module houses the memory required for program and data storage, and
its associated memory together with serial communication, I/O and suitable
programming interfaces. The standard memory can be increased by adding a plug-in
memory expansion board to the main system board. A battery is fitted to the module so
that the contents of RAM and the integral real time clock are retained when the mains
power supply is switched off. Expansion board memory is battery backed while plugged
into the module.
The front panel of the processor module carries the connectors for the two Serial
Communications Ports, the two FIP Communication Ports and the Printer/Programming
Connection Port. The access cover for the memory support battery is also located on the
front panel. Twelve LEDs are positioned on the front panel; two green LEDs indicate the
status of the watchdog, while ten yellow LEDs provide five pairs of outgoing and
incoming serial communication and FIP network connection indicators.
The front panel also houses a three-position key switch, providing halt, program and
normal positions; this is an aid to security and safety, and protection against external
program corruption. A four-character alphanumeric display provides improved
diagnostics, imparting information such as controller status and faults to the user.
1.4.2. Power Supply
The power supply module provides the power required for all of the modules contained in
the controller subrack, including the basic and verification I/O modules. A limited power
capacity may be available for consumption elsewhere in the system, e.g. additional I/O
modules in an I/O subrack. However, if the power requirement of any additional I/O
modules exceeds the available remaining current, further power supply modules will be
required. In the case of a 400S or Enhanced system incorporating a Fast I/O Driver,
additional Fast I/O Modules always require additional power supplies to be fitted. See
chapter 7 for details
1.4.3. Backplanes
The Backplane assembly is a PCB (printed circuit board) which carries connectors and the
associated circuitry for the processor module and the power supply module. The I/O
highway is extended on to the backplane that is fitted with one Basic and one Verification
I/O ribbon connector. The backplane also carries a terminal block for various external
connections, e.g. watchdog circuits and auxiliary outputs from the power supply.
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