The Front-End Software
of the DSS
Stefan Lüders, EP/SFT & IT/CO
DSS Advisory Board, March 17th 2003
Outline
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The PLC Cycle
The Front End Software
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March 17th 2003
Code Structure
The DSS Process Code
The DSS Monitoring Code
An Example
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Remark
This is the Front-End Software V0.9:
 It is NOT really fancy nor expert friendly.
It can’t be. The HMI is the Back-End.
 Dimensions of arrays, functionalities, …
might change. The sizes of the data blocks have
direct impact on the cycle time. Optimization
has NOT been done yet.
 Some functionality is NOT even appreciated and
will be hidden in the final implementation or by
the Back-End.
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The PLC Main Cycle
The PLC Main Cycle (OB1):

PLCs continuously monitor the
sensors
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e.g. temperatures, water flow,
sub-detector status
PLC:
Main cycle
T>Tthres
T>Tthres
T>Tthres
AND
Alarm
Input values are compared to
defined thresholds.
Several conditions can be logically
combined. Their fulfillment will
produce an alarm.
Alarms will trigger defined actions. Input: Sensors
Output: Action
Actions are on a coarse level (e.g.
(e.g. switching off power)
cutting power to a complete sub-detector).
End-of-Cycle
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The Code Structure
DIN
DB DIN
AIN
DB AIN
ALE
DB ALE
ALM
DB ALM
A2A
DB A2A
ACT
DB ACT
PROC status
PLC status
DSU status
DSS status
March 17th 2003
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PROC status
PLC status
DSU status
DSS status
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The DSS process code consists of six
levels running inside the main cycle.
Each level acts on a corresponding
data block (“data driven approach”)
Four different DSS monitor code
routines check the status.
All status are stored in additional DBs.
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Data Blocks
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The #entries are fixed at compile time.
Each entry corresponds to e.g. a DIN, AIN, a
logical function, an alarm, an action.
Sections:
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State of the entry, e.g. its value, unused flag,
error flags
Parameter, which can be set by the BackEnd, e.g. inhibits, acknowledges, resets,
trigger, enable / disable entry
Relations to DBs of lower levels, e.g. of an
ALM to DIN, AIN or ALE. Relations are
transmitted by the Back-End via a special
receive buffer to keep consistency.
Collected status of all entries, e.g. an entry
has gone off, is inhibited, is in error state
All DBs are different.
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How a Routine looks like…
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All routines are written in a FORTRAN /
PASCAL like language (“SCL”).
Each routine uses the DB structure, i.e.
loops on all used entries.
State values are determined according
the specific rules on relations and
parameters. Errors, inhibits,
acknowledgements, trigger, resets etc.
are considered.
The collected status is managed.
Entries might be enabled or disabled.
The latter only, if the entries has NOT
gone off.
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The DSS Process Code
DIN/AIN:
Reading and checking digital and analog inputs
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ALE:
Evaluation of different logical functions with
DIN and AIN as inputs
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ALM:
Evaluation of a logical AND with DIN, AIN and
DIN
DB DIN
AIN
DB AIN
ALE as inputs.
ALE
DB ALE
ALM
DB ALM
A2A
DB A2ATriggering of alarms, managing of
ACT
DB ACT
acknowledges and the alarm sound
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A2A:
Relations between alarms and actions
PROC status
PROC status
PLC status
PLC status
DSUACT:
DSU status
status
DSS status
DSS status
Execution of actions, managing of resets
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Digital INputs
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DIN
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AIN
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ALE
Digital values are sampled from
the I/O modules before OB1 starts.
DB DIN
Only used channels are considered
(to save time, DIN are processed
DBgroups
AIN
in
of 16).
Faulty modules / channels are
flagged.
The behavior on error
DB ALE
must be defined by the GLIMOS:
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ALM
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A2A
TriggerOnError,
BeGoodOnError,
InhibitOnError.
DB ALM
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ACT
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DB A2A
DIN
can be inhibited or triggered.
Value changes are notified to the
DIN
history buffer (size currently
DB ACT
fixed to 1000 entries)
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Analog INputs
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DIN
AIN
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Analog values are sampled during
the AIN routine. Only used
channels are considered.
The value is compared to…
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ALE
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ALM
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A2A
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ACT
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upper and lower thresholds, the
so-called Virtual AIN (VAIN),
physical boundaries and the
previous value, to detect faulty
sensors.
The behavior in case of an error,
inhibits or trigger is the same as
for DIN.
Changes of a VAIN are notified in
the AIN history buffer.
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ALarm Evaluation
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DIN
The DIN, AIN and VAIN can be
combined by four functions:
4fold AND, 4fold OR
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2 of 3
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analog value comparison
Each function has its own DB.
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AIN
ALE
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ALM
The access is done by an unique
addressing scheme, e.g.
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A2A
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ACT
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DIN: [1…8192]
AIN: [8193…10240,-8193…-10240]
Access errors, i.e. the access to
unavailable or unused entries are
notified and treated as inhibited.
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ALarM Trigger
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DIN
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AIN
The DIN, VAIN and ALE are
combined by a 8fold AND (t.b.c.).
Again access via the unique
addressing scheme, e.g.
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ALE
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ALM
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A2A
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ACT
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ALE (AND): [10241…11264]
ALE (2of3): [12289…13312]
Access errors are again notified
and treated as inhibited.
ALM can be acknowledged at any
time. The alarm is reset after all
actions have been executed and
the 8fold AND results FALSE.
ALM can be inhibited or triggered.
Changes of an ALM are notified in
the ALM history buffer.
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A2A and ACT
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DIN
AIN
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ALE
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ALM
A2A
ACT
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Each ALM can start several
actions with different delays (up
to 600 seconds in steps of 10s).
A pending A2A inhibits the reset
of the corresponding ALM / ACT.
ACT executes the action on the
hardware.
ACT can be reset, if no A2A are
pending and the corresponding
ALM has been acknowledged.
The behavior in case of an error,
inhibits or trigger is the same as
for DIN.
Changes of a ACT are notified in
the ACT history buffer.
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The DSS Monitor Code
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DIN
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Every status is collected in a corresponding DB.
The status is determined by…
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AIN
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ALE
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ALM
The PROC, DSU and DSS status are queried
every second.
The PLC status is queried…
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A2A
PROC status
PLC status
DSU status
ACT DSS status
March 17th 2003
event-based interrupts in case of coming / going
failures
periodic interrupts to queries specific information
every second for the H-CPUs
every minute for the communication
every hour for all modules
All statuses are queried at warm or cold start,
when the system enters the redundant mode
or on Back-End request.
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PROC status
PLC status
DSU status
DSS status
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The DSS Monitor Code
“PROC” is based on the
collected state of the DBs.
PROC status
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“PLC” monitors the CPU /
ET crates and the communication to the OPC server.
PLC status
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Errors are persistent and
must be reset.
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Fatal errors harm the
PROC chain. Some I/Os
are unprocessable.
DSU
status
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“DSU”
monitors all entities
inside a DSU.
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wraps up all of the
DSS “DSS”
status
above and provides an alive
signal.
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PROC status:
PROC
status
Channel / module error
Access / Value error
Alarms, Actions
Inhibits
PLC HW / SW status:
PLC
status
Warm / Cold starts
Power failure
Module failure
I/O access error
Redundancy error
CPU memory mismatch
CPU timing error
OK flag
DSU status:
DSU
status
PS / UPS status
CPU / ET crate status
DSS status:
DSSAlive
status
signal
PROC status
PLC status
DSU status
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An Example
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DIN
AIN
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ALE
ALM
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A PT100 (ET #4, Module #2, Channel #1, HW addres
#1024) is monitoring the temperature of a bottle of wine.
The upper threshold is set to 30°C (SORRY!).
If T>30°C “ValueTooHigh” goes off and leads to an alarm.
After 20s, the action (ET #4, Module #3, Channel #1, HW
address #257) is triggered. The action can be reset if the
alarm has been acknowledged.
Remarks: Positive safety is currently NOT applied here.
And the Back-End will NOT allow for delayed actions.
A2
ACT
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