Can SOMEONE change MXI-2 SYSRESET* de-assert time (now 2^24 cycles, but need ~2^96 (about 4 seconds)?) when used with external clock?

[Greg_Williams]

I'm using a Rubidium clock to drive a VXI-MXI-2 External Clock. Unfortunately, the rubidium source inhibits it's output for about 2 seconds. The MXI-2 SYSRESET* line is de-asserted "2^24 cycles" after turn-on (about 800ms). My system locks up before the rubidium is ready! I need to change the period that the MXI-2 asserts the SYSRESET* line to about 3 seconds, 4 to be sure. Any ideas? It would be NICE if NI could change the MXI-2 operation to assert the SYSRESET* line until the Ext Clk was stable (when used in the Ext Clk mode). Any help is appreciated, Thanks in advance.

[Josh_KNH]

Hello Greg,

Unfortunately, the timing of the VXI-MXI-2 cannot be adjusted to support a longer SYSRESET* assertion. I would first suggest that you check with the manufacturer of the Rubidium clock device since it is a VME spec. requirement that any device needing a longer SYSRESET* should actually assert that line directly itself (Permission 5.4 of the VME spec).

Despite that, if it were possible, NI would have gladly provided a method to lengthen the SYSRESET* assertion if reasonably possible. However, after reviewing the hardware design, I have verified that adjusting the timing of the SYSRESET* line is not physically supported on the VXI-MXI-2. Short of redesigning the hardware (we checked thoroughly), the board simply cannot adjust it's own SYSRESET* asertion t
ime.

I recognize that having the flexibility to do this would indeed resolve your situation, and I have filed a request that R&D consider this feature in future designs to accomodate out-of-spec. devices.

Unfortunately, I also recognize that this doesn't resolve your situation now, but again, the device manufacturer would be a better place to start so that they can correct the operation of their board.

Best Regards,
Josh Hernstrom
VXI Product Support Engineer
National Instruments