PXI 5112 synchronization skew

[moshe ben-david]

I am using a 1042 PXI chasis with 8186 controller and five 5112 cards. I and synchronizing the cards via the star trigger and seen an inter card skew of 6 nano second as opposed to the specified skew (less than 1nSec). What could be the reason for that skew?

[Adam_U]

The skew you are seeing may be due to the trigger specification for 5112 synchronization. The system reference clock has a maximum skew rated at <1ns but the trigger skew specification is <10ns. If the skew you are seeing is between triggers, this may be the problem. The samples should still be synched if you are using the same system reference clock. If so, you could delete the extraneous samples off of the front of the waveform and then have a functional skew of <1ns.

The High Speed Digitizer user manual is linked below.
http://digital.ni.com/manuals.nsf/websearch/998C51E969F4900486256D9F007103F2?OpenDocument&node=132090_US

Hope this helps,
-Adam

[moshe ben-david]

Does that mean that PXI-5112 can not distribute the trigger to other cards via the star trigger lines with a skew less than 1nSec?
Currently I am using the following triggering protocol:
5112 at slot 2 as master: it recieves external trigger via the PFI1 port and uses the PXI 10MHz clock as a reference clock. A clock sync pulse is sent over the RTSI0 line to the other cards.
The other 4 5112 cards are defined as slaves and getting the trigger from the PXI star trigger line and the PXI 10MHz clock as reference. The clock sync pulse is delivered via the RTSI0 line.
As I understand this configuration should give a skew less than 1nsec, unless the 5112 could not drive the star trigger line.
What am I doing wrong and what is the correct triggering pro
tocol to be used in order to achieve a skew less than 1nSec.