ADC VrefH to Vddad - MCS08DZ60

[a_serbouti1]

Hello,

I hope i´m now in the right forum!

I´m using the ADC 10 Bit of S08DZ60 to convert a voltage in the intervall from 0,5 to 4,5V.

In the Watch window I get maximally 910 and not the supposed 1024.

in this uC the Vrefh ist connected to Vddad und Vrefl to VSSad so that I can´t use any

voltage divider.

My question is how to get it with software?

I have read the datasheet but still can´t get it!

I´ll be merciful for any help or advices.

regards!

Added p/n to subject.

Message Edited by NLFSJ on 2008-06-30 02:26 PM

[a_serbouti1]

Hello,

i´m using the 64 Pin _uC.

Vref H & L are external, but I´m using the Board EVB9S08DZ60.

I still don´t find where to connect the both.

[allawtterb]

If the board you have is this one:

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=EVB9S08DZ60_128&fsrch=1

It looks like your board has an option for providing a seperate Vrefh, J105 should be moved from 1-2 to 2-3 to use a user defined Vrefh.  This will connect Vrefh to pin 9 of J104. 

[allawtterb]

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ADC VrefH & VrefL wrote:

Hello,

I hope i´m now in the right forum!

I´m using the ADC 10 Bit of S08DZ60 to convert a voltage in the intervall from 0,5 to 4,5V.

In the Watch window I get maximally 910 and not the supposed 1024.

in this uC the Vrefh ist connected to Vddad und Vrefl to VSSad so that I can´t use any

voltage divider.

My question is how to get it with software?

I have read the datasheet but still can´t get it!

I´ll be merciful for any help or advices.

regards!
Message Edited by NLFSJ on 2008-06-30 02:26 PM

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You must be using either the 32 or 48 pin package of the DZ60, the 64 pin package has external connection for Vrefh and Vrefl.  You can't get the output of the ADC itself to get any higher than ~910 if the input voltage is 4.5V and your Vdda is 5V.  You can rescale the value if you want but I am assuming you will need to scale the value from 910 to some other value anyway so there is no reason to do so.  Rescaling isn't going to give you any resolution back either, if you are only varying 4V (0.5V to 4.5V) and the Vdda is 5V your range will be ~102 to ~920.