Using Input and Return Vectors with Onboard Variables
This table gives additional information about how to use input and return vectors in conjunction with onboard variables. The following table lists VIs with more than one data parameter that require multiple variables when using vectors. The Maximum Variable Number column lists the highest variable number that a vector can point to and still have room for all the data without exceeding the total variable space. This table also contains notes that highlight a few special cases where the number of parameters does not equal the number of variables.
VI Name |
Vector Type |
Number of Parameters |
Number of Variables Required |
Maximum Variable Number |
Comments |
RPM and RPSPS are double precision floating point values (f64). They are internally represented in IEEE floating point format in two 32-bit variables. The first variable is the least significant, and the second variable is the most significant. This format is also used in the communications packet between the host computer and the NI motion controller.
While the three Arc VIs take double precision floating point values (f64) for their angle parameters, these values are converted to 32 bit values (i32 and u32) before being sent to the controller. Therefore, unlike other NI-Motion VIs taking floating-point values, the internal representation for each angle parameter requires only one variable.
The Circular Arc and Spherical Arc VIs are implemented identically on the NI motion controller. The VI simply substitutes zeros for plane pitch and yaw when you call the Circular Arc VI. When using variables and vectors, use the Spherical Arc VI exclusively.
The Read Limit Status and Read DAC Limit Status VIs return the forward and reverse status bytes (u8) packed together as one 16-bit word (u16). Only one variable is required.
The Read Trajectory Data VI returns two values (position and velocity) per axis. The total number of variable required is therefore two times the number of axes selected with the Acquire Trajectory Data VI.
The Wait on Condition VI can return two values, condition code and bitmapped status, to the variables specified with the return vector.