8051 assembly question
You can place the ADC_DATA in a ACC and the number (05h) in (B) register and use the multiply instruction (mul a,b) for multiplication and after the execution of this instruction you get the result in accumulator. and for division move the number (#0ffh) in (B) register and use (div a,b). if your result of multiplication is greater then 8 bits then your result will be placed in A and B registers and you should take care of it. you should handle the 16 bit division in 2 steps. like divide the number by 2,4 to bring it in the range of 8 bits. by shifting right and divide them in 2 or 4 steps.