There are many PC based solutions to digitize and play your message
backwards.
Is there a reason you can't do this?
Kirk

Jeff wrote in message
om...
Can anybody help me design a circuit that will digitize voice and
place the data into RAM, then read it and convert it back? The chips
from ISD won't work for my situation because there is no access to the
data. I want to be able to read the data in reverse to play the audio
backwards. I am going to have to use A/D and D/A converters and a PIC
microcontroller to do the job for me. My question is: Which is the
best A/D and D/A converters to use for a clear voice recording? What
should the sampling rate be? How many bits/resolution should I be
looking for? The PIC16F872 has a 10-bit A/D converter built in but I
am not well versed in Assembly Language and my BASIC compiler doesn't
support this function as far as I know. So, my thought is to build a
circuit around the PIC16F872 which will provide the address for the
RAM and sync pulse for the A/D converter. The converter will send
serial data to the RAM to store the recording. The PIC16F872 will
interpret which button is pushed by the user and access the RAM either
forwards or backwards (count up/ count down). Data will be sent to the
D/A converter and play the audio. Any suggestions?

Thanks.