HP E1433A User's Guide
The C-Language Host Interface Library
Upon entering the ARM state the HP E1433A starts saving new data in its FIFO. It remains in the ARM state until the Sync/Trigger line goes high. If the HP E1433A 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 HP E1433A continues to collect data into the FIFO, discarding any data prior to the pre-trigger delay. The HP E1433A 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 HP E1433A which encounters a trigger condition and is programmed to pull the Sync/Trigger line. If any HP E1433A is programmed for auto triggering (with e1432_set_auto_trigger), the Sync/Trigger line is pulled low immediately. The Sync/Trigger line may also be pulled low by an explicit call to the function e1432_trigger_measure.
Upon entering the MEASURE state the HP E1433A continues to collect data. The HP E1433A also presents the first data from the FIFO to the selected output port, making it available to the controller to read. The HP E1433A holds the Sync/Trigger line low as long as it is actively collecting data. In overlap block mode the HP E1433A 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 HP E1433A stops taking data only when the FIFO overflows. When data collection stops, the HP E1433A releases the Sync/Trigger line. When all HP E1433As are finished and the Sync/Trigger line goes high, the HP E1433A goes into the IDLE state again.
The measurement initialization and loop may be interrupted at any time with a call to e1432_reset_measure, which puts the module in the TESTED state.
Register-based VXI Devices
The HP E1433A 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.
You will not need to access the registers in order to use the HP E1433A. The HP E1433A’s functions can be more easily accessed using the HP E1432A Host Interface Library software. However, if you want more information about the registers see Appendix A: Register Definitions.
