Signal Input XY Mode

For each frame received, this mode provides the frame signals as a timestamp/value pair. This is the recommended mode for reading a sequence of all signal values.

The timestamp represents the absolute time when the XNET interface received the frame (end of frame), accurate to microseconds.

Use nxReadSignalXY for this mode.

The data consists of two two-dimensional arrays, one for timestamp and one for value.

Each timestamp/value pair represents a value from a received frame. When signals exist in different frames, the array size may be different from one signal to another.

The received frames for this mode are stored in queues to avoid signal data loss.

Example

In this example network, frame C is a cyclic frame that transmits on the network once every 2 ms. Frame E is an event-driven frame. For information about cyclic and event-driven frames, refer to Cyclic and Event Timing.

Each frame contains two signals, one in the first byte and another in the second byte.

The example uses CAN. The following figure shows a timeline of a frame transfer on the CAN network, followed by a single call to nxReadSignalXY. Each frame contains its name (C or E), followed by the value of its two signals.

The following figure shows the data returned from nxReadSignalXY. The session contains all four signals.

Frame C was received four times, resulting in four valid values for the first two signals. Frame E was received three times, resulting in three valid values for the second two signals. The timestamp and value arrays are the same size for each signal. The timestamp represents the end of frame, to microsecond accuracy.

The XY Graph displays the data from nxReadSignalXY. This display is an accurate representation of signal changes on the network.