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ADS7960: Clarify manual mode operation

dennis childs
Prodigy 20 points
Part Number: ADS7960

THE CHIP SPEC talks about N-1,N,N+1 and N+2 implying there is a single frame delay from selecting a channel
 to output of the channel, but Figure 1. implies a longer pipelined process

 First Frame the host sends the channel N on SDI - it takes four clocks for it to arrive
 Second Frame the device freezing the Analog channel at the second clock of a frame (from first frame (N)
 During second frame the analog channel settles until the second clock of the next (third) frame, 
 During second frame an Acquisition Phase starts on clock 14
 During third frame Conversion phase starts on clock 1, and completes on the 16th clock
 During fourth frame SDO shows the channel number N and the conversion results for channel N


 This means that to get the channels in order 0,1,2,3,...11 output 3,4,5,6,7,8,9,10,11,0,1,2

CAN YOU CONFIRM THIS IS HOW MANUAL MODE WORKS

  • 0
    TI__Expert 5485 points

    Hello Dennis

    In Frame n-1:

    -        The SDO output at this stage corresponds to the channel previously programmed by the user, which is lets say Ch_x1.

    In Frame n:

    -        The user makes the request to change the channel to Ch_x2.

    -        No change can take effect in this Frame since the command is still being received on SDI.

    -        The SDO output at this stage corresponds to the channel previously programmed by the user, Ch_x1.

    In Frame n+1:

    -        The change channel request made in Frame n, will now start to take effect. The mux will change the selected channel to Ch_x2, the analog input settles after the change and is ready to be sampled.

    -        The SDO output at this stage corresponds to the channel that was programmed by the user in frame n-1, and mux selected by the device in Frame n, and sampled at the start of this frame (Frame n+1), which is still Ch_x1.

    In Frame n+2:

    -        At the start of this frame, i.e. at the falling edge of CS, the analog signal mux selected in Frame n+1, that is Ch_x2 will now be sampled or latched.

    -        Within the same frame, the analog signal sampled by the ADC at the start of the frame is converted.  

    -        The SDO output at this stage corresponds to the channel that was programmed by the user in frame n, and mux selected by the device in Frame n, which is now Ch_x2.

    I hope this answers your question. Let me know if you need more information on this

    Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Prodigy 20 points

    Thanks for the fast response.  Was that a yes , confiirmed ,you get channel 0 when you request channel 3?

  • 0 in reply to dennis childs
    TI__Expert 5485 points

    Dennis

    I am not sure if i understand your last reply correctly.

    Lets say if you choose CH0 in current data frame by wirting on SDI,  then you will get conversion result of CH0 in (current + 2) frame. Same logic applies to subsequent input channel selection

    Thanks & Regards

    Abhijeet