GEM80-400 1. Introduction
Issue 3 04/99 ALSPA GEM80-400 CONTROLLER TECHNICAL MANUAL Page 1-7
1.4.4. Basic and Verification I/O Highways
The Basic and Verification Input/ Output Highways are medium speed, parallel, digital
highways used for transferring data between the controller and I/O modules or Operator
Input Units. Physically, these highways consist of 26-way ribbon cables which can be up
to 30 metres long, although loading restrictions apply beyond 10 metres.
The Basic and Verification I/O Modules are designed for connecting to such devices as
push-buttons, relays, lamps, solenoids, interlocks and limit switches. They provide an
interface between the controller circuits and plant-side circuits.
The Operator Interface Units comprise LCD units, thumb-wheel switches, etc., which
allow operators to input control commands to GEM
80 controllers and to monitor plant
status.
Full details of Basic and Verification I/O Modules and Operator Interface Units are given
in the relevant Product Data Sheets. Further information is also available in Chapter 3 of
this manual.
1.4.5. Serial Communication Links
Communication to GEM
80-400 Controllers and other peripherals, such as printers,
keyboards and other controllers, is most commonly achieved by using the GEM
80 ESP
(Extended Simple Protocol); other protocols are available. Further details can be found in
Chapter 4 of this manual and in the 'Serial Communications Manual', Publication
No.T457.
1.4.6. Printer/Programming Connection Port
A Printer/Programming Connection Port is provided on the front of the processor module.
A suitable GEM
80 programming tool, such as Gemesys 3, can load, dump or edit ladder
programs via this connection, or a printer can be connected directly to the controller.
1.4.7. Watchdog Contacts
Watchdog circuits and relay contacts provide a means of disconnecting the plant from the
controller and any I/O Subracks, hence shutting down the plant in the event of a serious
problem in either the plant or the controller. (See Chapter 11 for more details).
1.4.8. Fast I/O Driver
There is a wide choice of equipment for connection to the Fast I/O Driver. Applications
utilising the GEM
80-400 Enhanced Controller fall into the following categories:
(1) Analogue I/O
(2) Counter Inputs
(3) Extra Serial Communications Ports (Programmable Serial Communications 8847
allows data exchanges with almost any other mini, micro or mainframe computer)
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