HP 8-Channel 196 kSa/sec Digitizer plus DSP E1433A manual Channels and groups, Channel Groups

HP E1433A User's Guide

Using the HP E1433A

Channels and groups

This section gives some information about using channels and groups. For more detailed information see the HP E1432A help text.

Channel Groups

In the HP E1432A VXIplug&play driver, a channel group is the basic unit of hardware control. Any channel you want to control must first be assigned to a group with the hpe1432_createChannelGroup function. In addition to creating the group, this function returns a “handle” that uniquely identifies the group. You can then use this handle to direct functions to all channels in the group.

When you create a channel group, all input and tach channels in the group are automatically activated and all source channels are inactivated. But when you delete a channel group, input and tach channels are not automatically inactivated. Any input or tach channel that remains active after its group is deleted will continue to supply data to its module’s FIFO buffer during a measurement—consuming module resources. For this reason, you should always explicitly inactivate the channels in group before deleting it. You can inactivate channels with hpe1432_setActive. You can delete channel groups with hpe1432_deleteChannelGroup and hpe1432_deleteAllChanGroups.

Also when you create a channel group, channels which are not mentioned in the new group are not turned off. You must explicitly inactivate any channels you do not wish to be active. (An exception is a power-up when only the channels in the initial channel group are active.)

Initialization

The command used to initialize your system is hpe1432_init. This function initializes the VXIplug&play library and registers all HP E1433A modules. It also checks the existence of an HP E1432 module at each of the logical addresses given in the resource list and allocates logical channel identifiers for each channel in all of the HP E1432s. Input channels, source channels, and tach/trigger channels are kept logically separated.

Most other functions cannot be used until after hpe1432_init, but there are two functions which can be used before initialization to get information needed by hpe1432_init. These are hpe1432_find and hpe1432_getHWConfig. hpe1432_find searches the VXI mainframe and returns the VXI Logical Address for every HP E1433A found. hpe1432_getHWConfig returns additional information about the hardware.

After hpe1432_init has been run you can use hpe1432_getNumChans to get the total count of inputs, sources, and tachs for all HP E1433A modules named in the hpe1432_init call.

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