helo i want to know hao to make program conversion Digital to analog with AT89C51 and do you have list program or sofware?
I recommend to use a device with on-chip A/D converter. Take a look to: http://www.keil.com/dd/parm_search.asp and search for a device that has it. Also we provide extensive A/D example code on: http://www.keil.com/download/