Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 234 of 265
3
3
4
4
H
H
A
A
R
R
D
D
W
W
A
A
R
R
E
E
F
F
A
A
I
I
L
L
F
F
L
L
A
A
S
S
H
H
I
I
N
N
G
G
F
F
A
A
C
C
I
I
L
L
I
I
T
T
Y
Y
(
(
N
N
O
O
N
N
U
U
K
K
O
O
N
N
L
L
Y
Y
)
)
Hardware Fail Flashing is an integral part of the controller configured using various
hardware switches and/or links. The IC4 Configuration needs to be made aware of
whether Hardware Fail Flashing is required, although configuration data does not
enable or disable the facility.
If either processor or the hardware watchdog (see Section 33) shuts down the
controller, with the Hardware Fail Flash enabled, some traffic signals will flash while
the others are extinguished.
The hardware fail flasher can also be initiated by special conditioning, however
normal operation can only be re-instated by operator intervention (i.e. RFL=1 and
power off/on). Note that the part-time state can be configured to flash the signals
and this can be initiated and removed by special conditioning without operator
intervention.
34.1 ST900 Controller
If either processor or the hardware watchdog shuts down the controller with the ‘Non
UK Links’ fitted, the following sequence occurs:
1. The Green Lamp Supply relay is released - all Green signals are turned off;
2. Both SSR & Red/Amber Lamp Supply relays are forced on;
3. The Dim/Bright Relay released to force signals to their ‘Bright’ state;
4. All the Red, Amber and Green phase output latches on the Lamp Switch cards
are ‘Reset’;
5. ‘Flash Oscillator’ output enabled onto the Phase Bus. This may have a “steady
on period” at the start.
6. Either Red or Amber signals ‘Flash’ as selected on the Lamp Switch cards.
34.2 ST900 ELV Controller
For Hardware Fail Flash controllers, the HPU link is fitted between TP3 (Fail Flash)
and TP1 (Common). This allows the controller hardware to switch ON the lamp
supply to LSLS Card 1 and switch OFF the lamp supply to the other LSLS Cards.
The configuration set up by IC4 must include the hardware fail flash option. This re-
arranges the allocation of phase outputs, so that all outputs that are required to
flash are allocated to the first LSLS card. All the other outputs are allocated to other
cards. This means that an ST900 ELV controller with hardware fail flash must be
fitted with at least two LSLS cards.