Specifications

Engineering Standard –NSW
Signalling SMS 02
Cerberus Level Crossing Monitor Equipment
March 2005 Version 1.2 © Australian Rail Track Corporation Page 24 of 118
This document is uncontrolled when printed.
For complete details on the operation of the SCADA 2000 board refer
to the source code of the level crossing monitor and the SCADA 2000
A/2.0 Technical manual.
3.2.2.3 Software description
The level crossing monitor software consists of 3 separate tasks. A
task is essentially an independent piece of software that fulfils an
element of functionality.
Task 1 is the command task which:
 initialises the hardware and software,
 responds to commands received by either serial port,
 reports status changes assuming a Hayes Compatible modem is
connected to serial port A.
 Task 2 is the scan task which:
 Flash Led 4 each time it runs,
 reads and check the real time clock,
 toggles watch dog,
 scans digital inputs and logs changes,
 scans analogue inputs and logs changes,
 scans timers, updates timer status, and logs changes,
 evaluates logic expressions,
 scans intermediate states and logs changes,
 scans output states, sets outputs accordingly, and logs changes,
 update status, and flag status changes,
 checks serial port A modem is not off-hook and idle for too long,
 scans and logs serial port connection
changes. Task 3 is the serial communications
task which:
 receives characters from either serial port,
 assembles the received characters into messages,
 acknowledges messages which comply which the protocol,
 passes valid messages to Task 1.
 transmits messages passed from Task 1.
Command task description