Fast control using hardware timed single point timing

[jwf]

So, the problem goes away in a different PXI-1042 chassis.  The PXI-1042 backplane is entirely passive from a PCI standpoint. It is just copper wires and doesn't have many components to break. The PCI bus itself is a very robust and mature technology.

Speculation about what could be going wrong:

• Are you using PXI_CLK10?  PXI_CLK10 is generated by the backplane and if the backplane is misbehaving then perhaps the peripherals are working slowly as a result. This is about the only active thing that the backplane does on the PXI-1042 chassis. Could look at this with an oscilloscope to test.
• The PXI-1044 or 1045 chassis have PCI bridges, if using one of these, you could look into possible PCI bus issues.
• There could be a power supply issue; perhaps excessive noise. This could be causing the controller and/or peripheral to misbehave resulting in the bad performance. Could swap power supply shuttles to test this theory and see if the bad results follow the power supply shuttle.
• There could be, I suppose, a pin in one of the slots that is intermittent. This pin might be in contact often enough so that the system works marginally, but with a lot of errors that would slow things down. We could detect this with a logic analyzer. Are there any empty slots in the chassis? If so, perhaps move the cards around a bit to look for bad slots. Also, look at the backplane with a flash light to see if there are any noticeably bent or damaged pins.

I am assuming that the peripherals appear to be working, but just not as fast as in the other chassis. I mean, the test gets good data, just much more slowly than in the 'good' chassis.

Jason

PXI Hardware Engineer

[Stuart_G]

I just wanted to chime in on this.  It is VERY important that you disable USB from the BIOS.  With LV 8.2 there are actually 2 USB settings.  The one in the BIOS disables legacy OS support, and the one in the ini enables/disables the Pharlap native USB driver.  The MOST important one to disable is the one in the BIOS.  It is a little confusing I know.  What it breaks down to is actually a 2x2 matrix.  Setting the ini setting to True automatically disables the one in the BIOS (which is good), but setting the ini setting to False (again this is the Plap driver not the OS USB support) doesn't have any affect on the BIOS.  If you want MAXIMUM performance you need to disable the bios AND set the ini flag to false.  In practice though, for the rates you a looking at settng the ini entry to TRUE should be sufficieint. 

Hope this helps

StuartG

[AcqirisUser]

Hello Stuart,
Do you mean disabling the Lagacy USB support? This is the only USB reference I found in my RT8196. If I disable this option, does it mean my USB keyboard is longer seen at startup? I use the keyboard just in case I need to go into bios at startup and I don't want to get locket out with no means of getting back to the controller again. Thanks.

[Stuart_G]

I do mean disabling the legacy USB support.  In terms of your keyboard I think if you enable the Pharlap support for USB then you should be able to use it, but to be honest I have never tried it.  I always get a USB to PS2 converter and use it that way (or just grab an older non-USB keyboard).  I have an 8176 though and I'm not sure what the 8196 comes with in terms of ports.  But, I do know if you want fast rates you have to disable legacy USB.

StuartG