CMRR is common mode rejection ratio. it is the ratio of Differential gain to common mode gain. CMRR=Ad/Ac

Do you mean CMRR? If so, it means Common Mode Rejection Ratio.

CMRR measures how well a differential input will reject a common mode signal (common mode means the same signal applied to both differential input leads at the same time). The ratio is expressed in decibels (dB).

Nope, but DD600 does.

increase the efficiency of the system

mode-1(16-bit timer) i.e to run the timer from 0000 to ffff(hex) it takes 71milli seconds maximum in one cycle. but u can generate what ever the delay you wish on 8051. formula is (required delay/71ms)=x. now repeat the the above loop for x times you can get your desired delay.