Posted: Thu Nov 26, 2009 11:43 am Post subject: A4D4: slave mode and external clock
is it possible to use slave mode together with an external clock?
Like: I request a datapoint and get it after the next external clock pulse has arrived?
Set an analog out and it is processed at the next external clock pulse?
How to do this? In a Visual C++ sample program (VC_Slave_A4D4), I tried to replace the property tsSoftware by tsExternal, but this does show no effect (timebase has been reset to TIIExternalClock). Using this timebase for streaming works fine.
The Chico maps its registers into memory on the application, so a slave access is like a memory read. The system stretches this out to account for the nature of the PCI bus, but holding a memory access out potentially forever could result in problems.
So I'm believe that the slave access does a read from the ADC register, that in external clock mode may or may not have been recently updated. You would have to poll to watch for changes in value, or have some other means of knowing when to read the value for it to work.
There is a mode where you can do a slave access using the stream engine but even then this access would not be synchronized with the external clock update. _________________ Chris Smith
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