To further customize the block for use in your application, you can configure filtering,
feedforward inputs, tracking inputs, setpoint and output limiting, PID equation structures, and
block output action. Table 7-27 lists the PID block parameters and their descriptions, units of
measure, and index numbers, and Figure 7-15 illustrates the internal components of the PID
function block.
Table 7-27 PID Function Block System Parameters
ACK_OPTION 46 None Used to set auto acknowledgment of alarms.
ALARM_HYS 47 Percent The amount the alarm value must return to within the alarm limit be-
fore the associated active alarm condition clears.
ALARM_SUM 45 None The summary alarm is used for all process alarms in the block. The
cause of the alert is entered in the subcode field. The first alert to be-
come active will set the Active status in the Status parameter. As soon
as the Unreported status is cleared by the alert reporting task, another
block alert may be reported without clearing the Active status, if the
subcode has changed.
ALERT_KEY 04 None The identification number of the plant unit. This information may be
used in the host for sorting alarms, etc.
ALG_TYPE 74 None Selects filtering algorithm as Backward or Bilinear.
BAL_TIME 25 Seconds The specified time for the internal working value of bias to return to the
operator set bias. Also used to specify the time constant at which the
integral term will move to obtain balance when the output is limited
and the mode is AUTO, CAS, or RCAS.
BIAS 66 EU of OUT_SCALE The bias value used to calculate output for a PD type controller.
BKCAL_HYS 30 Percent The amount the output value must change away from the its output
limit before limit status is turned off.
BKCAL_IN 27 EU of OUT_SCALE The analog input value and status from another block’s BKCAL_OUT
output that is used for backward output tracking for bumpless transfer
and to pass limit status.
BKCAL_OUT 31 EU of PV_SCALE The value and status required by the BKCAL_IN input of another block
to prevent reset windup and to provide bumpless transfer of closed
loop control.
BLOCK_ALM 44 None The block alarm is used for all configuration, hardware, connection fail-
ure, or system problems in the block. The cause of the alert is entered
in the subcode field. The first alert to become active will set the active
status in the status parameter. As soon as the Unreported status is
cleared by the alert reporting task, and other block alert may be report-
ed without clearing the Active status, if the subcode has changed.
BLOCK_ERR 06 None This parameter reflects the error status associated with the hardware or
software components associated with a block. It is a bit string so that
multiple errors may be shown.
BYPASS 17 None Used to override the calculation of the block. When enabled, the SP is
sent directly to the output.
CAS_IN 18 EU of PV_SCALE The remote setpoint value from another block.
CONTROL_OPTS 13 None Allows you to specify control strategy options. The supported control
options for the PID block are Track enable, Track in Manual, SP-PV Track
in Man, SP-PV Track in LO or IMAN, Use PV for BKCAL OUT, and Direct
Acting.
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