Create Hex code for DTMF project.

Hi, I require hex code to flash to a pic chip for a dtmf remote project. I would like to use a standard 8870 dtmf decoder IC to monitor an audio source for dtmf tones in order to operate a relay via a pic chip & transistor for simple switching on / off. The operating codes required are 51# for ON and 510 for OFF. The output should always power up with the relay in the OFF position. Once turned ON the relay should turn OFF automatically after 3 minutes if it has not been turned OFF manually using the 510 tone. Ideally I would like to use an 8 pin pic chip eg: 12F629 / 12F675 / 12F683? but if this is not possible then a 16F628A. If a 16F628A is used then I would like to add a second output but without the time out function just ON & OFF, any 3 character codes could be used for ON & OFF for this output. The PIC could share the OSC of the 8870. The 51# & 510 tones are 75ms in length - I can send the dtmf audio files if required for reference. Hope you can help :o) Regards Mike.