Kirk Humphries

A/D wrap around vs conversion sequence length

Discussion created by Kirk Humphries Employee on Jan 30, 2006

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Posted: Fri Jul 22, 2005  3:06 am

 

So currently I am working with the A/D on the S12X but I believe the A/D module is similar on the S12 as well.

 

I am operating the A/D in multiple-channel, continuous conversion mode. After rereading the users guide several times I am still confused as to the difference between the wrap around channel select in the ATDCTL0 register and the conversion sequence length in the ATDCTL3 register. I am starting my conversions with channel 0 by setting C[D:A] to 0x0 in ATDCTL5. I am operating in non-FIFO mode. It seems to me that the starting channel(C[D:A]) in combination with the wrap around channel setting provides the same information as setting the starting channel and the conversion sequence length.

 

I know I am misunderstanding something but after rereading the documentation multiple times I can't figure it out.

 

Thanks.

 


 

Posted: Thu Jul 28, 2005  3:12 am

 

I got no answer on this so I thought I'd throw it out again to see if I get any replies this time.

 


 

Posted: Thu Jul 28, 2005  4:36 pm

 

> It seems to me that the starting channel(C[D:A]) in combination with

> the wrap around channel setting provides the same information as

> setting the starting channel and the conversion sequence length.

 

Doesn't wrap around mean that it will repeat the conversion continuously? Without it, you can trigger the sequence (one set of multiple inputs) when you are ready.

 

I use wrap around (or continuous) so that I don't have to keep starting the sequence every time I want to read status of my hand controller pots.

 


 

Posted: Thu Jul 28, 2005  11:41 pm

 

> > It seems to me that the starting channel(C[D:A]) in combination with

> > the wrap around channel setting provides the same information as

> > setting the starting channel and the conversion sequence length.

>

 

> Doesn't wrap around mean that it will repeat the conversion

> continuously? Without it, you can trigger the sequence (one set of

> multiple inputs) when you are ready.

>

 

> I use wrap around (or continuous) so that I don't have to keep

> starting the sequence every time I want to read status of my hand

> controller pots.

 

Hey,

 

Well I understand the continuous conversion sequence mode and yes, it is as you described above. My question, however, was specifically about the necessity of certain control bits that I described in my original post. Basically, I don't understand the purpose of WRAP[3:0] in the ATDCTL0 register. To me it seems that this provides redundant information that I am providing via other registers as I detailed in my original post. I'm sure that in reality this isn't redundant information so I am looking for feedback from anyone who might know the answer.

 

Thanks,

 


 

Posted: Fri Jul 29, 2005  8:42 pm

 

It wouldn't be like the 9S12. ATDCTL0 is not even used in the ATD_10B8C guide (listed for 9S12). Even the 9S12X device guide refers to that document by name, but the version for 9S12X is not listed when I look at all documents. See http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC9S12XDP512

 

So, how does one get the new documentation?

 


 

Posted: Fri Jul 29, 2005  10:39 pm

 

Try

 

http://www.freescale.com/files/microcontrollers/doc/data_sheet/MC9S12XDP512V2.pdf

 

Chapters 7 and 8. It appears that the MC9S12X family ATD is considerably changed from the MC0S12C32 ATD.

 


 

Posted: Sat Jul 30, 2005  2:08 am

 

Yeah I have that documentation and am indeed referring to the S12X. I guess most people here just got their hands on the S12X so I'll have to wait a while for people to play with it. I've had the S12X for over a year so I guess I'm a little too eager.

 

Thanks for your help.

 


 

Posted: Mon Aug 1, 2005  10:33 pm

 

> I hope this helps.

 

That certainly helps! I'll play around and see if I can get away with

only setting one or the other and let you all know what happens. Again

thanks for the information.

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