OK....so that makes me want to ask...since I've been contemplating this....look up tables in 16F parts. Been doing some experimenting, and I think you have to modify the PCL to do it on these parts (done it with 18F but its built in there) but it seems like it always makes the code jump to wierd areas and never works correctly. Anyone have a piece of code they might be willing to share? This is...for a thermister lookup in a sense....hitting certain temps I need to add an offset to a counter value. I dont need each value of the A/D, just jumps in increments of anywhere from 25 to 10 depending on the value. But I suppose I would need each value there, and then load an offset based on the A/D value being looked up in the table. Harold Hallikainen wrote: I designed the M700 and M750 "cow thermometers" at http://www.gla-ag.com . We used a 20 bit LTC ADC driving a PIC over SPI. The ADC has an internal reference, though not super precise. However, as others have pointed out, the ADC is ratiometric, so as long as the sample varies with the reference, errors cancel. I use a 0.1% resistor between the reference output of the chip and the top of the thermistor (with the bottom of the thermistor going to ground). I used the resistance tables supplied by the thermistor manufacturer. I put them in a spreadsheet and calculated what the ADC output would be at each temperature they specified. I then did a lookup table in the PIC with linear interpolation between the two points where the ADC value landed. Accuracy is better than 0.1degree C or 0.1degree F in the temperature range of interest (90 to 110 degrees F). Harold -- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available! -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------------------------- Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist