Description

Function description

This function block allows the selection of setpoint value types used in the servoloop:

Setpoint value type	Explanation
Remote setpoint (SP_RSP = 1)	The Setpoint comes from a block external calculation using the input RSP (remote setpoint). The input value RSP leads to the SP output.
Local setpoint (SP_RSP = 0)	The setpoint must be modified directly by the user (Local setpoint). In this operating mode the output SP is not entered using the function block, the variable attached to the SP is modified by the user.

and can be configured as additional parameters.

Properties

The function block SP_SEL has the following properties:

The switchover between the setpoint values can be bumpless
Operation with adjusting setpoint values if the controller is in manual mode
Upper and lower limit of the setpoint value used

Representation in FBD

Representation:

Representation in LD

Representation:

Representation in IL

Representation:

CAL SP_SEL_Instance (RSP:=RemoteSetPoint, 
    SP_RSP:=TypeOfSetPoint, PARA:=Parameters, 
    PV:=ControlledVariable, MA_I:=OperatingMode, 
    SP:=SetPoint, LSP_MEM=>LocalSetPointMemory, 
    STATUS=>StatusWord)

Representation in ST

Representation:

SP_SEL_Instance (RSP:=RemoteSetPoint, 
    SP_RSP:=TypeOfSetPoint, PARA:=Parameters, 
    PV:=ControlledVariable, MA_I:=OperatingMode, 
    SP:=SetPoint, LSP_MEM=>LocalSetPointMemory, 
    STATUS=>StatusWord) ;

Parameter description SP_SEL

Input parameter description:

Parameter	Data type	Meaning
RSP	REAL	Remote setpoint
SP_RSP	BOOL	Setpoint type used by the controller "1" : Remote setpoint "0" : Local setpoint
PARA	Para_SP_SEL	Parameter
PV	REAL	Variables to be controlled
MA_I	BOOL	Operating mode of the linked controller "1" : Automatic operating mode "0" : Manual mode

Input / output parameter description:

Parameter	Data type	Meaning
SP	REAL	Setpoint used by the controller

Output parameter description:

Parameter	Data type	Meaning
LSP_MEM	REAL	Local setpoint MEMory
STATUS	WORD	Status word

Parameter description Para_SP_SEL

Data structure description

Element	Data type	Meaning
sp_min	REAL	Lower threshold for setpoint used
sp_max	REAL	Upper threshold for setpoint used
bump	BOOL	During remote/local changeover: "1" : the SP output is forced with the value of LSP_MEM "0" : bumpless changeover
track	BOOL	"1" : the values of SP and PV are brought into line in manual mode (local setpoint only)
rate	REAL	SP increase during local/remote changeover in units per second (≥0)

Base	Lower limit	Upper limit
Hexadecimal	16#0	16#FFFF
Octal	8#0	8#177777
Binary	2#0	2#1111111111111111

Data	Representation in one of the bases
0000000011010011	16#D3
1010101010101010	8#125252
0000000011010011	2#11010011

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.