Read Variable

NI-Motion VI

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Read Variable

Reads the value of a variable and returns the result.

Device Compatibility

Device	Compatibility
7330	N
7340	Y
7344	Y
7350	Y
7390	N
NI SoftMotion Controller for CANopen—Accelnet	N
NI SoftMotion Controller for CANopen—Xenus	N

Var is the variable to read. Valid inputs are variables (0x01 through 0x78) and indirect variables (0x81 through 0xF8).

Board ID is a unique number assigned by Measurement & Automation Explorer (MAX) used to send and receive commands and data to or from a specific NI motion controller.

Ret Vect indicates the destination for the return data generated by this VI. Available return vectors include return data to the host (0xFF), return data to a variable (0x01 through 0x78), return data to an indirect variable (0x81 through 0xF8), and do not return data (0). Refer to Input and Return Vectors for more detailed information.

error in (no error) describes error conditions that occur before this VI runs. The default input of this cluster is no error. If an error already occurred, this VI returns the value of error in in error out. The VI runs normally only if no incoming error exists. Otherwise, the VI passes the error in value to error out. The error in cluster contains the following parameters:

	status is TRUE if an error occurred before this VI was called, or FALSE if not. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code.
	code is a number identifying an error or warning. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. Use the error handler VIs to look up the meaning of this code and display the corresponding error message.
	source is a string that indicates the origin of the error, if any. Typically, source is the name of the VI in which the error occurred.

Output is the value of the variable when Retn Vect = Return to Host (0xFF).

Bd ID Out is provided for flow control. You can string together NI-Motion VIs by wiring the Bd ID Out terminal of one VI to the Board ID terminal of the next VI.

error out contains error information. If error in indicates an error, error out contains the same error information. Otherwise, it describes the error status that this VI produces.

	status is TRUE if an error occurred, or FALSE if not. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code.
	code is a number identifying an error or warning. If status is TRUE, code is a nonzero error code. If status is FALSE, code is zero or a warning code. Use the error handler VIs to look up the meaning of this code and display the corresponding error message.
	source is a string that indicates the origin of the error, if any. Typically, source is the name of the VI in which the error occurred.

Using This VI

The Read Variable VI reads the value of the selected variable and returns it to the destination specified by the Ret Vect.

If the value of Retn Vect is set to Return to Host (0xFF), this VI also reads the value from the return data buffer and passes it back as output.

The condition codes are set according to the value read: GREATER THAN, LESS THAN or EQUAL to zero.

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