Description

Function description

The function block monitors the input variable X to detect whether it exceeds the upper limit or falls below the lower limit.

NOTE: If you only want to monitor the upper limit you can use the HYST_*** function block.

The data types for all input values must be the same.

and can be configured as additional parameters.

Available functions

The following blocks are available:

INDLIM_DINT
INDLIM_INT
INDLIM_UDINT
INDLIM_UINT
INDLIM_REAL

Representation in FBD

Representation:

Representation in LD

Representation:

Representation in IL

Representation:

CAL INDLIM_Instance (X:=Input, MX_HIGH:=MaxHighLimit,
    MX_LOW:=MinHighLimit, MN_LOW:=MinLowLimit,
    MN_HIGH:=MaxLowLimit, MX_IND=>ReachedHighLimit,
    MN_IND=>ReachedLowLimit)

Representation in ST

Representation:

INDLIM_Instance (X:=Input, MX_HIGH:=MaxHighLimit,
    MX_LOW:=MinHighLimit, MN_LOW:=MinLowLimit,
    MN_HIGH:=MaxLowLimit, MX_IND=>ReachedHighLimit,
    MN_IND=>ReachedLowLimit) ;

Parameter description

Input parameter description:

Parameter	Data type	Meaning
X	INT, DINT, UINT, UDINT, REAL	Input variable
MX_HIGH	INT, DINT, UINT, UDINT, REAL	Maximum upper limit
MX_LOW	INT, DINT, UINT, UDINT, REAL	Maximum lower limit
MN_LOW	INT, DINT, UINT, UDINT, REAL	Minimum lower limit
MN_HIGH	INT, DINT, UINT, UDINT, REAL	Minimum upper limit

Output parameter description:

Parameter	Data type	Meaning
MX_IND	BOOL	Display: Upper limit reached
MN_IND	BOOL	Display: Lower limit reached

EN stands for ENable; it is an optional block input. When the EN input is enabled, an ENO output is set automatically.

If EN = 0, the block is not enabled; its internal program is not executed, and ENO is set to 0.

If EN = 1, the block's internal program is run and ENO is set to 1. If an error occurs, ENO is set to 0.

If the EN input is not connected, it is set automatically to 1.

ENO

ENO stands for Error NOtification; this is the output associated with the optional input EN.

If ENO is set to 0 (because EN = 0 or in case of an execution error):

the status of the function block outputs remains the same as it was during the previous scanning cycle that executed correctly;
the output(s) of the function, as well as the procedures, are set to "0".

REAL

The REAL type is encoded in a 32 bit format.

The possible value ranges are shown in the figure below:

When a result is:

between -1,175494e-38 and 1,175494e-38, it is considered to be a DEN;
less than -3.402824e+38, the symbol -INF (for - infinity) is displayed;
greater than +3.402824e+38, the symbol INF (for + infinity) is displayed;
undefined (square root of a negative number), the symbolNAN is displayed.

NOTE: The IEC 559 standard defines two classes of NAN: the silent NAN (QNAN) and the signaling NAN (SNAN). A QNAN is a NAN with a most significant fraction bit while an SNAN is a NAN without a most significant fraction bit (bit number 22). QNANs can be propagated via most arithmetic operations without throwing an exception. As for SNANs, they generally indicate n invalid operation when they are used as operands in arithmetic operations (see %SW17 and %S18).

NOTE: When a DEN (non-standardized number) is used as an operand, the result is not significant.