Specifications
ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 213 of 265
29.4 Ports
The ports of the controller provide a means of connecting the hardware of the input
and output signals to the controller software.
Each port normally consists of 8 bits (0 to 7) which must be either all inputs or all
outputs.
In order to calculate the number of ports that are required, the inputs and outputs
are allocated, where practical, into groups of 8. It is better for configuring if all the
detectors for one phase are on the same port. UTC inputs must be allocated
different ports to detector or other inputs for software reasons.
29.5 Port Allocation
The controller firmware can use up to 31 I/O ports, numbered 0 to 30, giving a total
of 248 I/O lines numbered 0 to 247.
Each I/O port normally contains 8 input lines (for detectors and push buttons, etc.)
or 8 output lines (for UTC reply bits, etc.), although there are only 4 outputs on the
24 Input / 4 Output variant of the Serial I/O Card. The I/O card number is set by a
rotary switch on each card.
Always refer to the works specification / IC4 printout for the I/O used by a particular
installation.
29.6 Detector Fault Monitoring (DFM)
DFM is allocated to specified detector inputs and, if required, pedestrian push-
button inputs. Also see:
Section 7.3.4 for the monitoring applied to pedestrian on-crossing detectors,
Section 7.4.5 for the monitoring applied to pedestrian kerbside detectors, and
Section 16.2.15 for the monitoring of priority vehicle detectors.
With the DFM facility, if an input does not change state and remains permanently
active or inactive for a specified period, a DFM fault has been confirmed and the
following happens:
The cabinet alarm is illuminated, see section 30.1.4.
Optionally, the input can be forced active or forced inactive.
Entries will be made in controller’s fault logs.
DFM faults can only be cleared if the controller has seen the input change state
since reporting the fault. If the input has remained permanently active or inactive
since the fault was reported, the DFM fault cannot be cleared.
Accepting DFM Faults: If the detector fault cannot be immediately repaired, the DFM
fault can be ‘accepted’ by entering the handset command ADF=1. The cabinet alarm
will then be extinguished, allowing further faults to be indicated.