Logic Solver Cause and Effect Matrix function block execution

Each EFFECTn output has a corresponding STATEn parameter. EFFECTn can be either 1 (Normal) or 0 (Tripped). STATEn can have one of six values shown in the following figure. The arrows in the figure show the possible transitions between state values during normal operation.

Figure: State Transition Diagram for STATEn Parameters

The values that STATEn can assume depend on whether EFFECTn is Tripped or Normal. The following table shows the combinations that can occur.

After an initial download or a restart of the Logic Solver card, the initial value of every EFFECTn is Tripped. An effect remains Tripped as long as any causes associated with that effect are tripped. After all associated causes clear the effect become Normal.

The default behavior of the block is for EFFECTn output values to be a function of the value and status of the CAUSEn inputs. EFFECTn Trips when one or more CAUSEn associated with it is active.

You can modify this behavior with the LSCEM block's parameters in a number of ways:

• Use DELAY_TIMEn to set a delay time for EFFECTn to transition to Tripped.

• Use RESET_PERMITn to require an operator reset to transition EFFECTn to Normal. RESET_PERMITn can be set from process feedback or it could be a manual operator reset, such as from a key switch.

• Use START_PERMITn to force STATEn to Waiting for Start Permit, which prevents EFFECTn from becoming Normal unless START_PERMITn is True.

• Use FORCE_PERMIT to allow forcing of effects.

• Use FORCE_OPTS to allow forcing effects without FORCE_PERMIT being True.

• Use FORCE_OPTS to allow forcing multiple effects simultaneously.

• Use FORCE_EFFECTn to set EFFECTn to Tripped or Normal.

  Note

  It is recommended that you use the FORCE_EFFECTn parameters to manipulate final elements only when the process is not running.

• Use CAUSE_MASK to prevent selected causes from becoming active.

If all you require is simple, time-based sequencing, use DELAY_TIMEn to prevent EFFECTn from going directly to Tripped when an associated cause becomes active. While DELAY_TIMEn is greater than 0 (zero) STATEn is Trip Initiated - Delayed, which keeps EFFECTn Normal.   

To require an operator reset before an effect can return to Normal, use REQUIRE_RESETn, RESET_PERMITn, and RESETn. When REQUIRE_RESETn is True, EFFECTn remains Tripped when an associated cause is active. How STATEn transitions depends on RESET_PERMITn.

If RESET_PERMITn is True (the default value), STATEn transitions from Tripped directly to Ready to Reset. Configure RESET_PERMITn to False to make STATEn transition from Tripped to Waiting for Reset Permit. The reset permit can be written from process feedback or set by an operator from a key switch or other hardware device. When RESET_PERMITn becomes True, STATEn transitions to Ready to Reset. From here, setting RESETn to True transitions STATEn and EFFECTn to Normal.

Use START_PERMITn in a similar way to require permission to transition STATEn from Waiting for Start Permit. The default value of START_PERMITn is True, which allows the transition. If START_PERMITn is False and associated causes are cleared, STATEn transitions from Tripped to Waiting for Start Permit. To move STATEn and EFFECTn to Normal, set START_PERMITn to True.

Use a combination of FORCE_PERMIT, FORCE_OPTS, and FORCE_EFFECTn  to force EFFECTn to a desired value. To force effects you must first either set FORCE_PERMIT to True, or select the FORCE_OPTS option Force permit is not required to force Effects. Changing FORCE_PERMIT from True to False removes current forces.

The parameter LATENT_TRIP is True when:

• FORCE_PERMIT is required to force an Effect (FORCE_OPTS option Force permit is not required to force Effects is not selected)

• ACTIVE_CAUSESn is non-zero

• FORCE_EFFECTn is Force Normal

If LATENT_TRIP is True, setting FORCE_PERMIT to False trips Effects that have been forced to Normal.

Setting FORCE_EFFECTn to Force Trip immediately transitions EFFECTn to Tripped even if DELAY_TIMEn is configured. Setting FORCE_EFFECTn to Force Normal immediately transitions EFFECTn to Normal, regardless of any configured recovery strategy. If STATEn is Trip Initiated-Delayed, setting FORCE_EFFECTn to Force Normal returns STATEn to Normal.

When CAUSEn is in a trip condition DELAY_TIMERn begins counting down. If you set FORCE_EFFECTn to Force Normal, then set it back to Do Not Force, DELAY_TIMERn resets and begins counting down again.

You can manipulate FORCE_EFFECTn from runtime interfaces. Manipulating FORCE_EFFECTn from within a module is not likely to be useful. Use the FORCE_OPTS option Forcing of multiple Effects is allowed to set whether multiple effects can be forced at the same time.

FORCE_OPTS includes an additional option: Force permit control should be visible in operator interface. Select this option if your force effect control is in an operator display. Do not select this option if you are using a key switch or other manual means to force effects.

Manipulate the parameter CAUSE_MASK to prevent one or more causes from becoming active under certain process conditions. Setting a bit in CAUSE_MASK to True prevents the corresponding CAUSEn from tripping any associated effects. If after an effect is tripped CAUSE_MASK masks the causes that tripped that effect, STATEn transitions out of Tripped. The state it transitions to depends on the configuration of the block parameters FORCE_EFFECTn, START_PERMITn, REQUIRE_RESETn, and RESET_PERMITn. Manipulate CAUSE_MASK using a Calc/Logic block based on process conditions, for example, the current batch phase. Do not manipulate CAUSE_MASK directly from runtime interfaces. To bypass process conditions use upstream voter blocks instead.

The OVERRIDESn parameter indicates if EFFECTn is being overridden. The OVERRIDESn values are:

• None 

• Forced to Tripped 

• Forced to Normal

• All associated Causes masked

ACTIVE_CAUSESn indicates the currently active causes that are associated with EFFECTn that are not masked in CAUSE_MASK. FIRST_OUTn indicates the cause or causes that first tripped EFFECTn. If additional causes become active, FIRST_OUTn does not change. FIRST_OUTn retains its value until EFFECTn returns to Normal.

For example, if CAUSE2 becomes active and EFFECT1 trips, ACTIVE_CAUSES1 and FIRST_OUT1 are both set to 2. If CAUSE3 (which is also associated with EFFECT1) subsequently becomes active, FIRST_OUT1remains 2 and ACTIVE_CAUSES1 becomes 6 (bits 2 and 3 of ACTIVE_CAUSES1 are set).

The following table summarizes the state-dependant conditions necessary to transition EFFECTn  value between Tripped and Normal.

The following descriptions and tables explain each state and the conditions necessary to transition to other allowable states. Note that the value of the RESETn parameter is set to False at the end of every execution independent of the current value of STATEn.