Question

b) What is the main purpose and requirement of REFS O and REFSİ bit in ADMUX register for using ADC in AVR? why interrupt technique is preferred over poling technique in AVR programming? Why lower byte TCNTIL of timer 1(16-bit timer counter register) is required to be read first then TCNT1H?

Answer 1

Answer :- b) Reference Selection Bits are used to select the reference voltage for ADC. There are three different ways of selecting reference voltage. The bits, REFS1 and REFS0 is used to select the reference voltage.

Answer :- c) Polling technique makes code to stop at a particular place and other part of code can't be run while polling is in process.
Whereas interrupt method allows code to run continuously and run a specific part of code (ISR) on interrupt. After finishing the ISR, the code again runs continuously.

Answer :- d) We read TCNT1L first to read accurate 16-bit value. When we read lower register value the higher register value is kept in a temporary register. Thus this method is used to read both TCNT1H and TCNT1L at the same time.