Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 23 of 118
This document is uncontrolled when printed.
The I/O Board also has two serial communications ports at the front, and
a Bitbus communications port which is connected to the Backplane.
Dimensions of the I/O Board are 261 mm (length of face plate) x 220 mm
(d) x 20 mm (width of face plate). These are the standard dimensions for
a 6U high x 220 mm deep extended Eurocard.
The major features of the I/O Board are:
a) The 8044 BitBus Enhanced Micro controller (BEM) which is the heart
of the I/O Board, controlling all its functions.
b) EPROM socket (U5) which allows a 64 KByte (27512) EPROM
containing the software to be installed.
c) RAM sockets (U6 & U7) which each contain a 32 Kbyte SRAM chip.
d) Two D9 Male serial ports (Channel A & Channel B) which are
controlled by the 82530 serial communications chip.
e) 14 x Indication LEDs on the front of the board (LEDs 1 - 2 are for the
micro controller status, LEDs 3 - 6 are general purpose LEDs, and
LEDs 7 - 14 show the I/O Port Configuration).
f) Two 64 way IEC Male connectors mounted on the rear of the board.
These connectors contain the power supply pins, BitBus pins, I/O pins
and Address pins. The top connector is known as 'IOJ1' (it has I/O Bit
Nos. 1 to 32) and the bottom connector is known as 'IOJ2' (it has I/O
Bit Nos. from 33 to 64).
Drawing M08-723 shows the physical dimensions and component layout
of the I/O Board. Drawing M08-724 shows a block diagram of the I/O
Board.
3.2.2.1 Function
The I/O Board is responsible for controlling the functions of the Level
Crossing Monitor and storing the logged information.
3.2.2.2 Operation
The microprocessor on the I/O Board executes a software program which
resides in the EPROM plugged into the I/O board. The program determines
the functionality and configuration of the Level Crossing Monitor.
If the program is not executed correctly then a Watch Dog IC will reset the
board. The Watch Dog IC also monitors the 5 volt power supply and will
reset the microprocessor and hold it reset while the 5 volts bus is not
greater than 4.7 volts. There have been some cases where a slightly high
resistance connection between the power supply and the I/O board supply
pins has resulted in the Watch Dog resetting the microprocessor and
stopping the monitor from operating.