NI PXI-2557 8×1 Multiplexer (SP8T) Topology

The following figure represents the NI PXI-2557 in the 8×1 multiplexer topology.

Making a Connection

Call the niSwitch Connect Channels VI or the niSwitch_Connect function to connect channels in this topology. If applicable, you must call the niSwitch Disconnect Channels VI or the niSwitch_Disconnect function to disconnect an existing connection before you call the niSwitch Connect Channels VI or the niSwitch_Connect function.

Note  The niSwitch Disconnect Channels VI or the niSwitch_Disconnect function does not operate the relay until the next niSwitch Connect Channels VI or the next niSwitch_Connect function is executed. Thus, one channel of the 8×1 multiplexer is always connected to the common channel. If you have reset the module or called the niSwitch Disconnect All Channels VI or the niSwitch_DisconnectAll function, you do not need to disconnect the default channel (ch0) from COM upon initial connection.

The following sequence of tasks illustrates the VI/function calls necessary to make consecutive connections—one between CH 1 and COM and the other between CH 2 and COM:

1. Call the niSwitch Connect Channels VI or the niSwitch_Connect function with parameters ch1 and com.
2. Call the niSwitch Disconnect Channels VI or the niSwitch_Disconnect function with parameters ch1 and com.
3. Call the niSwitch Connect Channels VI or the niSwitch_Connect function with parameters ch2 and com.

When scanning the NI PXI-2557, a typical scan list entry might be ch1->com;. This entry routes the signal connected to CH 1 to COM.