Specifications

RailCorp Engineering Manual — Signals — Equipment Manual
Cerberus Level Crossing Monitor Field Equipment Manual TMG E1261
© RailCorp Page 21 of 89
Issued August 2012 UNCONTROLLED WHEN PRINTED Version 2.1
Log changes in serial port connections.
Turn led 4 off.
Serial communications task description
Execution of this task is commenced by task 1. It then proceeds in the following manner:
Initialise variables.
Continuously repeat the following:
If a serial port interrupt has occurred then
Acknowledge the interrupt to the Serial Controller Chip.
Read the Serial Controller Chip interrupt status register.
Repeat the following until their are no more interrupts to be processed.
a) If a serial port A receive interrupt occurred then turn led 5 on, check for and
process any reception errors, and process the received character.
b) If serial port A transmit interrupt then if there are characters to transmit, send
the next one, otherwise clear the interrupt.
c) If serial port A external status interrupt then turn on led 6 and check the state of
carrier detect. If it is on, set the port A communications link flag, and enable
RTS, CTS flow control. If it is off, clear the port A communications link flag,
store the connection lost time, and disable RTS, CTS flow control. Reset the
external status interrupt.
d) If a serial port B receive interrupt occurred then turn led 5 on, check for and
process any reception errors, and process the received character.
e) If serial port B transmit interrupt then if there are characters to transmit, send
the next one, otherwise clear the interrupt.
f) If serial port B external status interrupt then turn on led 6 and check the state of
carrier detect. If it is on, set the port B communications link flag, and enable
RTS, CTS flow control. If it is off, clear the port B communications link flag,
store the connection lost time, and disable RTS, CTS flow control. Reset the
external status interrupt.
Else if their has been no serial port interrupt for 1 second, then check the
transmission/reception state for each serial port and if they are not idle take the
necessary corrective action.
2.2.2.4 Configuration & Set-Up
A specific EPROM is prepared and labelled for the particular level crossing. The EPROM
is inserted in U5. The EPROM must be type 27512 running at 200nS or better.
A DALLAS DS1235YWL 200nS or better is inserted in U6.
A DALLAS DS1244Y 200nS or better is inserted in U7.
The links for the board must as follows (all others shall be open circuit, that is removed):
1-2 3-4 5-6 7-8 10-11 12-13 17-18
19-20 25-26 27-28 29-30 31-32 33-34 37-38