I have nmo expereince with the ADC0808 (although I am sure its not complicated) but the DAC0808 is a perfectly simple device to operate: It converts whatever 8-bit digital value you apply to its input port (pins 5-12)into a current value using a 2R network. So all you have to do is to connect pins 5-12 to Px.0 -Px.7 where 'x' is some port on your 8051 or 8255 unit. You will have to add an I/V converter at the output (pin 4) of the DAC.

But I have actually seen a working circuit, where my friend had applied a constant current source to the output pin 4, and was getting a variable *voltage* output between the reference voltage pins (14 and 15) !! It worked perfectly.... Amazing!

If u need it I will explain in detail how I had interfaced the dac0808... if I can find it I will mail you the circuit diagram I had used.

kundi