ACE1553-3U-4 Hardware Manual
21
4.1.3 Star Trigger
The PXI backplane defines specific layout requirements so that the star trigger lines provide
matched propagation time from the star trigger slot to each module for very precise trigger
relationships between each module. The star trigger is a high-performance trigger signal, which
can synchronize all of the modules in a chassis. You can also synchronize the modules using
the normal PXI trigger bus, but the star trigger offers increased performance. Specifically, the
star trigger provides a skew of less than 1 ns and a delay between the star trigger slot and each
peripheral slot of no more than 5 ns.
To use the star trigger, a module with the ability to generate the star trigger must be placed in
Slot 2 of the chassis. Slot 2 is dedicated for the star trigger controller (although any standard
module placed in Slot 2 will function normally in an application where star triggering is not
required). Receiving modules must also be designed to be able to accept the star trigger.
The standard PXI trigger bus can perform the same functionality with a trigger signal from any
chassis slot, but with less precise timing.
The ACE1553-3U-4 card can use the PXI STAR input signal to perform a TTAG reset
(clear) to DAY 1. This TTAG reset to DAY 1 will work if the IRIG circuitry is running in
Free-Wheeling mode:
external IRIG signal selected, but no signal connected
PXI 10MHz System Clock connected to the IRIG decoder
The TTAG clear to DAY 1 can be either triggered via PXI Star signal or via PXI Trigger
Input 0.
Please NOTE:
the PXI Star signal on the backplane is ACTIVE LOW.
For electrical specification please refer to reference
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