General information about function blocks

Function block modes

Function block modes are described below. Supported modes vary with each function block. Some blocks support modes that are not supported in other blocks.

Out of Service (OOS): The block algorithm is not active. The output is maintained at the last value or at a specified failure action value.

Initializing Manual (IMan): The upstream block of a cascade pair is put into this mode when its downstream partner is in a non-cascade mode. This prevents the upstream block from closing the cascade. When the downstream block returns to a cascade mode (Cas or RCas), the upstream block leaves IMan and returns to its target mode.

Local Override (LO): The block is put into this mode when tracking is activated; the output is driven to a value other than that generated by normal block execution. When tracking is deactivated, the block returns to its target mode.

Manual (Man): The block output is set directly by the operator.

Automatic (Auto): In this mode, the control algorithm of the block is active. An operator-entered setpoint is used in the control algorithm to determine the block output.

Cascade (Cas): This mode is similar to Auto except that the setpoint is supplied by another function block through the CAS_IN parameter. The block maintains a back calculation output value (BKCAL_OUT) to provide bumpless mode transfer when the mode is changed.

Remote Cascade (RCas): This mode is similar to Cas except that the setpoint is supplied by an external control program through the RCAS_IN parameter. The block maintains a back calculation output value (RCAS_OUT) to provide bumpless transfer when the mode is changed.

Remote Out (ROut): This mode is similar to Man except that the OUT value is supplied by an external control program rather than directly by the operator. OUT is supplied through the ROUT_IN parameter. The block maintains a back calculation output value (ROUT_OUT) to provide bumpless transfer when the mode is changed.

The normal mode is the desired operating mode of the block that is set during configuration. Normal is meant to indicate that this is the mode in which the block should be operating during normal operation.

The target mode is the mode that is set manually or by another function during operation. These target modes must be listed during configuration as permitted modes for the block. IMan and LO are not selectable target modes. Unless you specify otherwise during configuration, the system assumes that you will write mode changes to the target mode field and read them from the actual mode field.

The following table lists the supported modes in specific function blocks. In addition, the Books Online information on individual function blocks lists the supported modes for that block.

Table: Supported modes for function blocks

Function block

Supported modes

Analog Input Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Analog Output Function Block

Initializing Manual (IMan)

Out of Service (OOS)

Local Override (LO)(1)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (Rcas)

Arithmetic Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Bias/Gain Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Local Override (LO)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (Rcas)

Control Selector Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Manual (Man)

Automatic (Auto)

Deadtime Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Device Control Function Block

Out of Service (OOS)(1)

Local Override (LO)(1)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (RCas)(1)

Discrete Input Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Discrete Output Function Block

Initializing Manual (IMan)

Out of Service (OOS)

Local Override (LO)(1)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (RCas)(1)

Enhanced Control Selector Function Block

Automatic (Auto)

Initializing Manual (IMan)

Manual (Man)

Out of Service (OOS)

Fuzzy Logic Control Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Local Override (LO)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (RCas)

Remote Output (ROut)

Input Selector Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Fieldbus Input Selector Extended Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Integrator Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Lab Entry Function Block

Out of Service (OOS)

Manual (Man)

Lead/Lag Function Block

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Manual Loader Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Local Override (LO)

Manual (Man)

Model Predictive Control (MPC)

Out of Service (OOS)

Initializing Manual (IMan)

Manual (Man)

Automatic (Auto)

Local Override (LO)

Model Predictive Control Professional (MPCPro)

Out of Service (OOS)

Initializing Manual (IMan)

Manual (Man)

Automatic (Auto)

Local Override (LO)

Cascade

MPC Process Simulator

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

H1 Carrier Multiple Discrete Input

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

H1 Carrier Multiple Discrete Output

Out of Service (OOS)

Initializing Manual (IMan)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Local Override (LO)

Remote Cascade (RCas)

Multiplexed Analog Input

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

Neural Network

Out of Service (OOS)

Manual (Man)

Automatic (Auto)

PID Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Local Override (LO)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (RCas)

Remote Out (ROut)

Ratio Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Local Override (LO)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

Remote Cascade (RCas)

Signal Characterizer Function Block

Out of Service (OOS)

Automatic (Auto)

Splitter Function Block

Out of Service (OOS)

Initializing Manual (IMan)

Manual (Man)

Automatic (Auto)

Cascade (Cas)

(1) These modes are only visible when the function block is extended to a fieldbus device.