Kirti Bhanushali

10 bit ADC issue with HCS08 microcontroller

Discussion created by Kirti Bhanushali on Jun 21, 2011
Latest reply on Jun 22, 2011 by bigmac

I am using  MCS08SG8  ADC in 10 bit  and continuous conversion mode.  I am facing certain issue while reading ADCR register only when the value is 0xFF. I found that whenever the analog voltage is 2.5V i.e. ADCR value is 0xFF, it is found that if the voltage varies by a few bits i.e 254 to 257, the ADCR register sometimes shows a few transients i.e. ADCR value becomes either 0 or HIGH. This behaviour is reported only at 2.5V and not at any other voltage. What could be the reason behind this s/w or h/w. I even tried using long sample time, but the issue continued to crop up even then.