Allen-Bradley Logix 5000 Controllers

This is a specific type of array fault encountered during the Sequential Function Chart (SFC) postscan process. When this fault is suppressed, the controller employs an internal fault handler to clear it, causing the postscan process to bypass the instruction that caused the fault and proceed to the next instruction. This behavior is active only when SFC instructions are configured for automatic reset.

This is a specific type of array fault encountered during the Sequential Function Chart (SFC) postscan process. When this fault is suppressed, the controller employs an internal fault handler to clear it, causing the postscan process to bypass the instruction that caused the fault and proceed to the next instruction. This behavior is active only when SFC instructions are configured for automatic reset.

This fault indicates that the Control Variable (CV) health is bad. This can be due to poor CV value quality, an invalid CV value, or a communication fault affecting the CV output. When true, CVFault indicates an error on the output module, and the PIDE instruction sets the appropriate bit in Status. The equivalent Sts_CVBad in the PPID instruction will also be set if Inp_CVIOFault is true.

This fault indicates an invalid previous Control Variable (CV) value. For PIDE, this occurs if CVPrevious is less than 0 or greater than 100, or outside CVLLimit/CVHLimit when in Auto or Cascade/Ratio mode. The instruction limits CVn-1. In the PPID instruction, Sts_CVPrevBad is set only if Inp_UseCVPrev is enabled (1) and Inp_CVPrev value is invalid; its allowed range is always between Cfg_CVEUMin and Cfg_CVEUMax.

This alarm indicator is set to true when the calculated rate of change for the Control Variable (CV) exceeds the configured CVROCLimit. It signifies that the CV is changing too rapidly. In the PIDE instruction, the status is set even if the rate of change is equal to the limit, despite the parameter description stating it is set only when exceeded.

This fault indicates that the Hand Feedback (Tieback) value health is bad. This occurs if the Hand FB value quality is bad, the value is invalid, or there's a communication fault with the input. In the PPID instruction, Sts_HandFdbkBad is also set if Inp_HandFdbk value is Infinite (Inf), Negative Infinite (-Inf), or Not-a-Number (NaN).

This fault is declared by the controller when internal module temperatures exceed a critical threshold, leading to a reset and immediate power disablement. The OK status indicator illuminates red, and the module remains unpowered until it cools below the Hardware Preservation Hysteresis limit. Subsequently, the module enters fault mode, logs the event, and displays 'CPU Temperature Fault' on the front panel. For 5580 controllers, this can be indicated by a flashing green OK status.

This fault indicates that the Process Variable (PV) health is bad. This can be due to an invalid input value, communication issues, poor signal quality, or the PV exceeding its Engineering Unit (EU) limits. In the PPID instruction, the equivalent Sts_PVBad status is set under these conditions, plus additional internal conditions not present in PIDE.

This fault indicates an invalid span configuration for the Process Variable (PV), specifically when PVEUMax is less than or equal to PVEUMin. In the PPID instruction, the equivalent Sts_ErrPVEU is set when Cfg_PVEUMin is greater than Cfg_PVEUMax, or if Cfg_PVEUMin or Cfg_PVEUMax is configured as Infinite (Inf), Negative Infinite (-Inf), or Not-a-Number (NaN).

This fault indicates invalid ratio clamping limits. This occurs when RatioLLimit is less than 0 or RatioHLimit is less than RatioLLimit for the PIDE instruction. The PPID instruction's Sts_ErrRatioLim is set when Cfg_RatioLoLim is greater than Cfg_RatioHiLim. Note that PPID does not set this error condition when Cfg_RatioLoLim is less than 0.

This alarm indicator is set to true when the current Setpoint (SP) value exceeds the configured Setpoint High Limit (SPHLimit). This indicates that the SP is attempting to go above its allowable maximum. In the PIDE instruction, this alarm is not evaluated if the SP limits configuration (SPLimitsInv) is invalid. In the PPID instruction, it is not evaluated if SP is not held by shed (Sts_SPHeld=0), SP is not set to interlock SP by shed (Sts_IntlkSP=0), or if SP clamping limits are invalid (Sts_ErrSPLim=0 implies valid, so Sts_ErrSPLim=1 would be invalid).

This alarm indicator is set to true when the current Setpoint (SP) value falls below the configured Setpoint Low Limit (SPLLimit). This indicates that the SP is attempting to go below its allowable minimum. In the PIDE instruction, this alarm is not evaluated if the SP limits configuration (SPLimitsInv) is invalid. In the PPID instruction, it is not evaluated if SP is not held by shed (Sts_SPHeld=0), SP is not set to interlock SP by shed (Sts_IntlkSP=0), or if SP clamping limits are invalid (Sts_ErrSPLim=0 implies valid, so Sts_ErrSPLim=1 would be invalid).

This fault indicates invalid Setpoint (SP) clamping limits. This can occur if SPLLimit is less than PVEUMin, SPHLimit is greater than PVEUMax, or SPHLimit is less than SPLLimit. If SPHLimit is less than SPLLimit, the instruction limits the value using SPLLimit. In PPID, Sts_ErrSPLim is set if Cfg_SPLoLim is less than Cfg_PVEUMin, Cfg_SPHiLim is greater than Cfg_PVEUMax, or Cfg_SPLoLim is greater than Cfg_SPHiLim.

This status bit is set by the PPID instruction when an invalid configuration of the Control Variable (CV) operating limits is detected. Specifically, it indicates that the configured maximum CV value (Cfg_CVHiLim) is set lower than the configured minimum CV value (Cfg_CVLoLim). Unlike the PIDE instruction, which silently limits CV, the PPID instruction explicitly flags this condition, preventing potentially erratic control behavior due to an illogical CV range.

An overflow occurred during the evaluation of a subscript expression. This condition generates a Major Recoverable Fault, indicating that an out-of-range condition exists within the expression's calculation. It may also be recorded as a minor overflow fault if enabled. Calculation of subscript expressions no longer silently produces invalid results, making this fault detection more predictable.

This specific code identifies a major recoverable fault, indicating that the controller's internal temperature has exceeded its defined major fault threshold. The fault is recorded in the major fault log and displayed on the front panel as 'T17:C34 CPU Temperature Fault'. If the fault is not cleared by a fault handler in the user program, the module will transition into fault mode.

This is a minor fault indicating that the controller's internal temperature is approaching its operating limit. It sets the Diagnostics minor fault bit and is recorded in the minor fault log, but it is not displayed on the front panel. The Diagnostics minor fault bit will clear if the temperature returns to an acceptable range; however, the minor fault record remains.