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Interfacing ADC_DSK6713 - Interrupt, Timing

Started by Martin J. February 1, 2007
Dear Group,

I am new in DSP processing and I am working on my diploma with DSK6713.I
am solving the problem of interfacing DSK to 16-bit ADC (AD7980). My
problem is probably very basic so could anyone give some clue or link
where to find more info? 

To set McBSPs I am using the BIOS.

I want to interface ADC and DSK as described (CS\ Mode 3-wire with busy
indicator).

          (Pull up resistor to VIO)
	       ^
               |
               |
             ------> IRQ\_HWI
            | 
            |  
  SDO -------------> DR1_McBSP1
  SCK <------------- CLKR1_McBSP1
  CNV <------------- TOUT_Timer1


Rising edge on CNV starts a conversion, selects the CS mode, and forces
SDO to high impedance. SDO is in high until the conversion is finished. 
CNV must be returned low before the minimum conversion time to generate
BUSY signal. When the conversion is complete, SDO goes low. This can be
used as an interrupt signal. Then ADC starts clocking out the data bits,
MSB first.

1) Using BUSY as an interrupt: 
When the conversion is complete, SDO goes from high impedance to low. How
to treat HWI procedure to process this interrupt and not get confused by
data bits coming on SDO in acquisition phase after BUSY signal? I thing if
a bit in the word in acquisition phase becomes 0 HWI will again treat it
like an interrupt.?

2) Setting the timer to use it for CNV is fine. The only thing I do not
know, if I wanted to use it with McBSP1 Frame sync pulses sent from FSR,
how to achieve shifting against each other (Frame/Timer1 pulses) by  e.g.
3 clock pulses?


So my problems are rather basic... how to recognize interrupt while other
actions happening on the same wire?
How to set up timer to be shifted with other timing source by 3 clock
periods?

Thanks very much.

Martin