Flowserve MX FOUNDATION Fieldbus Field Unit - Manual (Page 34)

MX/QX FOUNdaTION Fieldbus Field Unit FCd LMENIM2330-01 – 08/11
34
RCAS_OUT_D is a block setpoint and status provided to a supervisory host for back calculation and
to allow action to be taken under limiting conditions or mode change.
SP_D is the discrete target block output value (setpoint).
The Invert I/O option can be used to do a Boolean NOT function between the SP_D and the hardware.
The SP_D supports the full cascade sub-function. Cas mode must be used to transfer the output
of another block to the SP_D of the DO. There are additional I/O options which will cause the SP_D
value to track the PV_D value when the block is in an actual mode of LO or Manual.
Readback
If the hardware supports a readback value, it is used for READBACK_D, which, after accounting for
the Invert I/O option, acts as the PV_D for this block. If not supported, READBACK_D is generated
from OUT_D. The OUT_D and READBACK_D parameters both use XD_STATE. The PV_D and SP_D
use PV_STATE.
Supported Modes
O/S, LO, Iman, Man, Auto, Cas, and RCas. The Man mode can be used to force the output, in a PLC
sense.
Alarm Types
Standard block alarm.
Simulation
Simulation is used to support testing. Simulation can be enabled through the configuration tool and
allows the manual entry of the Readback Value and its Status. Alternatively the operator can change
the block Mode to Manual and adjust the Output Value.
This feature requires the installation of a hardware jumper on the MX/QX FF unit, located on header
X5 Pins 7 and 8.
3.7 Proportional Integral Derivative (PID)
Function Block
The Proportional Integral Derivative (PID) function block combines all necessary logic algorithms to
perform process control. The block supports mode control, signal scaling and limiting, feed forward
control, override tracking, alarm limit detection and signal status propagation.