Using a analog multiplexer through ADC0800, I input 10.2v and 10.2v to 8051, the microcontroller read these voltages as FFh and FFh respectively. My aim is to multiply these voltages and to convert it to decimal to get the original result, using SDCC complier. The result after multiplication is FF * FF = FE01 ie 01 in Accumulator and FE in B register.My aim is to obtain 104v decimal value. Tips to convert FF to 10.20v The FFh value is converted by multiplying FF by 4 (FF * 4=3FC), the result is 3FC h, and then divide it with 64h 3FC/64=A and 3FC % 64=20 , the quotient is Ah ie 10 decimal and remainder is 14h ie 20 decimal. Thus I obtained 10.20V.