Programming Analog Input Registers for MSeries NI-6221

Question

I am trying to understand the Preliminary M Series Register Map in order to correctly setup and acquire data from the Analog Input channels of my PCX-6221 card. I have been able to figure out the DIO locations and use them but I am having trouble understanding what I have to do to configure and acquire data using the Analog Input registers of the card. I need to program at this level for an RTX application using Microsoft Visual Studio Net 2003 and have had great success doing so with other NI Cards. I have tried looking at the examples provided by the MDDK but I haven't been able to create a environment that allows me to compile them with Chipobjects and it appears like alot of the work is hidden by the subroutines.
I wonder if someone had a high level algorithum using the Register Map it would help out alot.
Questions:
How would I create a multiple channel Scan List and load it into the card setting gain etc...
How would I configure the card to acquire continously at a specified freq (ex 1000 samples a sec)
How would I start/stop acquisition
I would guess getting the status of the FIFO and accessing the FIFO is a matter of reading the AI_STATUS_1 and AI_FIFO_DATA locations
Would looking at the Register Programming Manual for the "E" Series help me or just get me more confused?
Thanks in advance for any light you can shed on the subject.
Floyd

Answer 1

Hi Floyd-
Let me address your questions individually:
How would I create a multiple channel Scan List and load it into the card setting gain etc...
A multi-channel scanlist can be created as shown in the method aiConfigureChannel() from ai.cpp in the M Series MHDDK \Examples folder.  Note that the other operations leading up that point (notably, aiClearConfigurationMemory() must be performed in the order shown in the various AI examples.  aiex3.cpp is the most useful starting point for investigation, in my opinion.
How would I configure the card to acquire continously at a specified freq (ex 1000 samples a sec)
aiex3.cpp shows how to setup the device and its DMA controller (aka the "MITE") for DMA operation.  In order to configure for continuous operation you set the "continous" flag in that example to kTrue.  The effect of that setting is to program the STC-II to generate either a finite or continuous AI sample clock.  This programming is performed in the function aiNumberOfSamples() from ai.cpp and has the effect of setting the appropriate bitfield for continuous operation in the AI_Mode_1 register. 
Earlier in your post you asked if the STC Technical Reference Manual ( http://digital.ni.com/manuals.nsf/websearch/E929838D7D0EE50986256728007FEADF ) would be a good reference.  In fact, it's a great reference from the perspective of understanding the bitfield/register names and understanding the basics of how the timing hardware works (for example BC, UC and other sample counters are all functionally equivalent in the STC and STC-II).  From the perspective of actual register writes and reads, the functionality is different between E Series and M Series.  The biggest difference, as another forum user alluded, is that we map and write directly to the registers on M Series so Windowed_Mode reads and writes are no longer necessary.
Another difference between STC and STC-II is that the STC-II uses NI TIO-style counter/timers.  For that reason, the NI 660x RLP manual ( http://digital.ni.com/manuals.nsf/websearch/4CE1C778F442B01386256C870060F9F3  ) would be a good reference for M Series counter/timer operations.
How would I start/stop acquisition
Assuming you don't need an external start trigger, you only need to write to the strobe bit AI_Command_2->AI_START1_Pulse.  This will create a single start trigger pulse internally.  The differences between AI_START1 and AI_START are described in the STC Technical Reference Manual.
A finite acquisition would be stopped automatically by the AI timing engine based on the number of samples you program via the method shown in aiNumberOfSamples().  Continuous AI would be stopped by first stopping the DMA operation and then calling aiReset().
 I would guess getting the status of the FIFO and accessing the FIFO is a matter of reading the AI_STATUS_1 and AI_FIFO_DATA locations
Yes, this would work but I would strongly suggest using DMA as shown in aiex3.cpp.  If you want to use "programmed I/O" to read the FIFO data directly, that method is shown in aiex2.cpp
 Would looking at the Register Programming Manual for the "E" Series help me or just get me more confused?
In many cases it would be very helpful.  See my comments, above.
I have inherited code that works on 65xx cards which I am pretty sure uses windowed mode that I am using in this 6221 driver. I have found that I can set the PLL registers to act as DIO and I can read the Discrete inputs just fine. Makes me curious, if Windowed mode is not used doesn't that mean the addresses are relative to the BAR1 address? Why then am I able to read the DIO?
I'm not sure why this would work- it's possible that some legacy functionality is still working due to the way you access the hardware in your code.  For full functionality with M Series you must use mapped memory I/O to write and read from the device's registers.
Also starting with Clock_and_FOUT according to the example I set it for Slow_Internal_Timebase. But when I read back that Address it is always zero. According to the register map it is a "write". Does that mean I can't read it's contents? Or do I seem to have a problem because I am trying to use windowed mode with this card.
Yes, the "write" registers are write-only and the "read" registers are read-only.  The effect of data read from or written to "write" or "read" registers, respectively, is undefined.
Hopefully this helps-
Tom W
National Instruments