Issue 5 - September 2006
Page 21 of 65
Bit Reference Description
0
History
Entry in history table - errors logged relating to
processors and communications
1
Data/Voting
2oo3 voting error – voting discrepancies
encountered and logged by the processors during
I/O scanning
2
LFD
latent fault detection of failed on or failed off signal
paths – monitor and fault bits set depending on
fault type and location
3
Monitor
Initialisation error – bits are set in the fault or
monitor registers
4
INIT
System initialisation error – modules referenced in
the table of operations are missing. Either a single
slot module or both modules missing in a dual slot
hot repair partnership.
5
MPP A
Processor A failure – out of synchronisation
6
MPP B
Processor B failure – out of synchronisation
7
MPP C
Processor C failure – out of synchronisation
8
MPP A power
Processor A loss of power – fuse or PSU
9
MPP B power
Processor B loss of power – fuse or PSU
10
MPP C power
Processor C loss of power – fuse or PSU
11 MPP
low
Battery
Memory battery - low charge on one or more of the
processor’s batteries
12
Off-line module
Single slot repair - module off-line – should be on-
line.
13
Digital Output
Fault on any digital output module(s)
14
Multiple fault
Multiple faults on a module
15 Reserved
Table 1 FALT Error Flags (RTTS 8.30 versions 001 – 003)
The error flags should be used to give primary indication to the operator/maintainer that a fault
exists within the system. In addition to the error flags the chassis system power supply fault
contacts should also be wired to at least one digital input channel and used for system power
supply fault reporting. On the majority of systems other external fault indications would be wired
to digital input channels to provide maintenance alerts (eg cabinet temperature, field power
supply failure, loop fuse failure etc).
3.5.6.1 Bits 0 - History
Entries in the system History table – the errors in the history table are those related to the
processors and communications areas.
3.5.6.2 Bit
1
-
Data/Vote
Data (vote) entries – these errors are due to voting discrepancies encountered during the I/O
scanning. This bit is set by the main processors detecting errors and not the I/O modules and
therefore does not result directly in any other monitor/fault bits being set in the exception tables.
3.5.6.3 Bit
2
-
LFD
LFD entries – these errors are due to latent fault testing of the I/O modules. LFD testing is done
on each I/O module in turn on a 20 second rotating basis. Since genuine LFD errors are
detected by the I/O module they will result in the I/O module health lamp being turned off and
other bits in the monitor/fault flags being set eg if system channel A has a fault then the monitor
flag bit 1000h would be set. It should be noted that LFD testing is not carried out on an output
module that is detected as not being healthy. However, LFD continues on input modules after
