VXI manual Register-basedVXI Devices, VT1433B Users Guide Using the VT1433B, 3-28

VT1433B User's Guide

Using the VT1433B

Upon entering the ARM state the VT1433B starts saving new data in its FIFO. It remains in the ARM state until the Sync/Trigger line goes high. If the VT1433B is programmed with a pre-trigger delay, it collects enough data samples to satisfy this pre-trigger delay and then releases the Sync/Trigger line. If no pre-trigger delay has been programmed, it releases the Sync/Trigger line immediately. When all modules in a system have released the Sync/Trigger line (allowing it to go high), a transition to the TRIGGER state occurs.

Upon entering the TRIGGER state the VT1433B continues to collect data into the FIFO, discarding any data prior to the pre-trigger delay. The VT1433B remains in the TRIGGER state until it sees a high-to-low transition of the Sync/Trigger line. The Sync/Trigger line is pulled low by any VT1433B which encounters a trigger condition and is programmed to pull the Sync/Trigger line. If any VT1433B is programmed for auto triggering (with hpe1432_setAutoTrigger), the Sync/Trigger line is pulled low immediately. The Sync/Trigger line may also be pulled low by an explicit call to the function hpe1432_triggerMeasure.

Upon entering the MEASURE state the VT1433B continues to collect data. The VT1433B also presents the first data from the FIFO to the selected output port, making it available to the controller to read. The VT1433B holds the Sync/Trigger line low as long as it is actively collecting data. In overlap block mode the VT1433B stops taking data as soon as a block of data has been collected, including any programmed pre- or post-trigger delays. (It starts again when another trigger occurs). In continuous mode, the VT1433B stops taking data only when the FIFO overflows. When data collection stops, the VT1433B releases the Sync/Trigger line. When all VT1433Bs are finished and the Sync/Trigger line goes high, the VT1433B goes into the IDLE state again.

The measurement initialization and loop may be interrupted at any time with a call to hpe1432_resetMeasure, which puts the module in the TESTED state.

Register-based VXI Devices

The VT1433B is a register-based VXI device. Unlike message-based devices which use higher-level programming using ASCII characters, register-based devices are programmed at a very low level using binary information. The greatest advantage of this is speed. Register-based devices communicate at the level of direct hardware manipulation and this can lead to much greater system throughput.

Users do not need to access the registers in order to use the VT1433B. The VT1433B’s functions can be more easily accessed using the VT1433B Host Interface Library software. However, if more information about the registers are provided in Appendix A: Register Definitions for reference.

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