many PICs do not have hardware DAC. It is only when you move to newer and higher end chips, you get DACs.

however, many PICs have a comparator reference voltage generator for its comparators. Those generators typically have a resolution of 4 - 5 bits. Some of them can have their output (CVref) routed to an output pin. viola! you have a 4-bit dac.

here is an example of generating a ramp on 16F886.



(原文件名:16f886 4-bit dac.PNG)

now, this is nothing to write home about but if you are in need of some quick dac, it may work for you.

enjoy.