Spectrum 1734, User Manual

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4-10 Chapter 4: OE2CIH and HART
User’s Manual Pub. 0300272-03 Rev. B
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Low Clamp uses the Low Clamp Value (see below). If clamping has
been disabled, this setting is not allowed.
•
High Clamp uses the High Clamp Value (see below). If clamping has
been disabled, this setting is not allowed.
•
Hold Last State will lock the outputs to the last known value while
ignoring further changes to output words.
•
Program Value uses the value set by the user (see below).
Fault Value . This value determines the output during a fault condition. Fault
Value is a signed 16-bit integer. Values may range from 32767 to -32768. It may
not exceed the range set by the High/Low Clamp Limits if clamping is enabled
(see below).
The Fault Value is clipped to the range limits as follows:
•
0 to 20 mA: 0.0 mA to 21.0 mA
•
4 to 20 mA: 3.0 mA to 21.0 mA
Fault Conditions
Fault conditions are:
•
Watchdog Timeout
The watchdog timeout for the main CPU is set to 1 second. If it is locked
up during that time, the HART modem shall set the output to the
appropriate fault action. When the watchdog resets the main CPU, it will
hold both channels off and remain in this state and wait for user
intervention. If the CPU is severely damaged and the watchdog is non-
functional, the HART modem will remain in control of the output. (See
HF channel status bit in section in this manual)
•
Main CPU locks up, but HART modem CPU continues to run
If this condition exists after a successful configuration, the HART
modem CPU will set the output to the appropriate value based on the
Fault Action. This condition will not allow any updates to module or
channel status bits and I/O data due to the fact that the main CPU is non-
functional. A communications fault will exist in the rack for this module.
If this condition exists during power-up, the HART modem CPU will not
start and there will be no output. A communications fault will exist in the
rack for this module. If the MCU is functional enough to have its
watchdog fire, the Watchdog Timeout behavior shall take over (see
above).
•
Main CPU loses communication with HART modem CPU
If the main CPU loses communications with the HART modem CPU for
any reason, it will consider this a Hard Fault condition (see HF channel
status bit in section in this manual).
•
Communications Fault
If the connection is broken to the Point Bus adapter that the module
resides, the I/O connection will timeout and a Comms Fault condition
will be detected. The Fault Action for each channel shall be set.
Program Value
This value determines the output value while the system is not in Run mode.
Program Value is a signed 16-bit integer. Values may range from 32767 to -
32768. It may not exceed the range set by the High/Low Clamp Limits if