5/12/2017
TECH-538/D.W.O. 23160
Page 46 of 189
Fault State Configuration
Three failure scenarios with ICoT applications can be observed:
1.
During a power failure event
, the pneumatics (air supply, solenoid, actuator, tubing, etc.) should
ensure a fail-safe position is achieved. As the ICoT electronics will be turned-off, it is out of the
loop.
2.
During a communication failure event
, the ICoT didn’t lose the power (it is “turned on”) but it
may lose the setpoint sent by another block or another part of the control system. Thus it is able
to drive the valve to a pre-configured fault state / fail safe position. This also happens when there
is no communication with the LAS (master) to keep the network working.
3.
When an internal block failure
occurs, one of the blocks in the ICoT may present a fault
condition, bad status or is forced to Out of Service. This condition may also happen in normal
situations when the user is downloading a new configuration, for example. In this case a fault
state condition can also be configured.
It’s important to know that the Transducer block configuration takes precedence over the AO block. In
other words, the fault state in the AO block will only prevail if the Transducer block is not in fault state
condition.
According the Reference (FOUNDATION™ Specification, Function Block Application Process Part 2 – FF-
891, Rev FS 1.10) (Section 2.12 - Fault State Handling), the Fault State parameters determine the behavior
of an output block in one or more of the following conditions after exceeds timeout defined in the
FSTATE_TIME parameter:
•
loss of (or bad) communications detected in the CAS_IN;
•
There is a FS substatus in the CAS_IN when the target mode is CAS; or
•
There is a FS substatus in the RCAS_IN when the target mode is RCAS.
If one of these conditions exists, then the block will go to the configured Fault State.
Resource block fault state parameters
o
FAULT_STATE
parameter located in the Resource block indicates if the device is in a fault
condition.
o
SET_FSTATE
and
CLR_FSTATE
parameters can be used to force and clear the FSTATE
condition for maintenance and test purposes.
