MC_ReadParameter

This function block reads a numeric (LREAL) parameter value from the axis.
The command is typically processed synchronously.

Syntax

Definition:

FUNCTION_BLOCK MC_ReadParameter
VAR_INPUT
    Axis        : Type_PtpReadWriteParameter;
    Enable      : BOOL;
    ParameterId : EAxisParameterId;
    Mode        : EReadMode;
END_VAR
VAR_OUTPUT
    Valid       : BOOL;
    Busy        : BOOL;
    Error       : BOOL;
    ErrorId     : UDINT;
    Value       : LREAL;
END_VAR

Inputs

Name	Type	Default	Description
Axis	Type_PtpReadWriteParameter		Reference to the axis
Enable	BOOL		Triggers a read on rising edge (EReadMode.Once) or every cycle while TRUE (EReadMode.Cyclic).
ParameterId	EAxisParameterId	Invalid	Identifier of the parameter to read.
Mode	EReadMode	Once	Once: read once at rising edge of Enable. Cyclic: read every cycle while Enable is TRUE.

Outputs

Name	Type	Description
Valid	BOOL	Valid output available at function block.
Busy	BOOL	Function block is not finished. Always FALSE with ReadMode Once.
Error	BOOL	Error occurred within function block.
ErrorId	UDINT	Error identifier
Value	LREAL	Last successfully read value of the parameter.

Further information

Alternatively, the axis status can be read from the PLC using the AXIS_REF structure.

myAxis.McToPlc.Std.AxisState

Information about the individual states is summarized in the section State diagram.

Possible error codes

For this function block, the following values, among others, are possible for the ErrorId output:

Error(Hex)	Error(Dec)	Error type	Description
0x8145	33093	Function Block	Mapping of cyclic interface between NC and PLC is missing (e.g., AXIS_REF, AXES_GROUP_REF, ...). A reference used by the function block (e.g., to an axis, group, mover or other motion object) is not linked to the corresponding NC object, or its cyclic mapping is incomplete.

An overview of all NC error codes can be found here:

Other errors

Version information

TwinCAT Standard >= v3.1.4026.23.1
TF5500 MC3 Base >= v4.0.6