Owner's manual

6-3
Discrete Output (DO) Function Block
Setting the Output To set the output for the DO block, you must first set the mode to define
the manner in which the block determines its setpoint. In Cascade
mode, the setpoint equals the input value (CAS_IN_D). In Automatic or
Manual mode, the setpoint must be entered manually by the user. In
Remote Cascade mode, the setpoint is determined by a host computer
that is writing to the RCAS_IN_D parameter.
To further customize the output, configure the SP_PV Track in Man,
Invert, and Use PV for BKCAL_OUT I/O options.
NOTE
SP_PV Track in Man, Invert, and Use PV for BKCAL_OUT are the only
I/O options supported by the DO block. You can configure I/O options in
Manual or Out of Service mode only.
The SP_PV Track in Man option permits the setpoint to track the
process variable when the block is in Manual mode. With this option
enabled, the setpoint (SP_D) becomes a copy of the process variable
(PV_D), and a manually-entered SP_D value is overwritten on the
block’s next execution cycle. This option can prevent a state change
when transitional from Manual to Automatic mode. You can disable this
option in Manual or Out of Service mode only.
The Invert option inverts the setpoint (SP_D) before it is stored in
OUT_D. With this option enabled, OUT_D becomes an inverted copy of
SP_D. With this option disabled, OUT_D is a direct copy of SP_D. If
discrete output feedback is not supported by the field device, a copy of
OUT_D is used in its place (with a delay of one execution time) to
become READBACK_D. The readback value is processed through the
Invert option to become PV_D, which normally matches SP_D in Auto,
Cas, or RCas mode.
The Use PV for BKCAL_OUT option specifies that BKCAL _OUT equal
the value of the process variable (PV_D) instead of the setpoint (SP_D).
If you do not enable this option, BKCAL_OUT will equal SP_D.
Simulation With SIMULATE_D enabled, the specified value and status is reflected
in READBACK_D. If SIMULATE_D is not enabled, and the mode is not
OutofService, the value of OUT_D is sent to the hardware.
Action on Fault Detection To determine the state to which the output goes if the block is in CAS
mode and the CAS_IN input has a BAD status, configure the following
parameters:
FSTATE_TIME – The length of time that the AO block delays before
setting OUT equal to FSTATE_VAL upon the detection of a fault
condition. If the block’s target mode is Cascade, a fault condition will be
detected if the CAS_IN has a BAD status, or an Initiate Fault State
substatus is received from the upstream block.
FSTATE_VALD – The value to which the OUT_D attribute transitions
if the length of time specified in FSTATE_TIME passes and the fault
condition has not cleared. You can configure the channel to hold the
value at the start of the fault action condition or to go to the Fault
Action Value (FAULT_ACTION_VAL).