topic adc conversion time setting in S12 / MagniV Microcontrollers

adc conversion time setting

jyothipusuluri — Wed, 21 Jan 2015 05:39:21 GMT

Hi all, for xep100 micom, how to achieve adc conversion time of 3.2us?(please suggest me how to calculate conversion time from ATD clock cycles,if my prescale value is 3,sample time scale 000,ADC resolution is 12bit) jyothi Pusuluri

Re: adc conversion time setting

kef2 — Wed, 21 Jan 2015 15:00:04 GMT

You didn't specify ATD clock source frequency, so I can't suggest specific figures. Check table A-15 ATD Operating characteristics and note 2 under that table. For 12bits resolution, conversion time (including sample time) is from 20 to 42 ATD clock cycles. That's num of sample time clocks + 16. When discharge (SMP_DIS) is enabled, conversion time takes longer, plus additional 2 ATD clock cycles.

12bits: sample clocks + 16 + SMP_DIS*2

10bits: sample clocks + 15 + SMP_DIS*2

8bits: sample clocks + 13 + SMP_DIS*2

Hope this helps.

Re: Re: adc conversion time setting

iggi — Wed, 28 Jan 2015 13:09:13 GMT

Hi,

The total conversion time can be calculated as follows:

Total Time = conversion time + sample time + discharging time

Conversion time:

12bit resolution: 16 ATDCLK cycles

10bit resolution: 15 ATDCLK cycles

8bit resolution: 13 ATDCLK cycles

Sample time: can be set in range 4 – 24 ATDCLK cycles

Discharging time:

If bit SMP_DIS in ATDCLT1 register is set then it takes 2 ATDCLK cycles.

If SMP_DIS is 0 then it takes 0 ATDCLK cycles.

So, min/max times in case of 12bit resolution is:

Minimum time = 16 + 4 + 0 = 20 ATDCLK cycles

Maximum time is: Time = 16 + 24 + 2 = 42 ATDCLK cycles

ATDCLK can be set in range 0.25 – 8.3MHz.

Depending on the MCU bus clock and equation to calculate the ATD clock which is:

fATDCLK = fBUS / 2×(PRS + 1)

you can easily calculate ATDCLK cycles in microseconds.

Regards,

iggi