It's only about a year since I was enthused by the PIC16F628A with its
2K ROM and 224 bytes of RAM opening up more possibilities for the RAT series of projects.Well Microchip have added several more devices to their 18/20 pin range offering more RAM, more ROM, more EEPROM, low power operation, and with precision internal clock options which allow up to 3 more I/O lines.
PIC16F648A like the 628A but with 4K ROM and 256 bytes RAM and 256 bytes EE. Cost is $1.87 for 100 off.
PIC16F87 4K ROM, 368 bytes RAM, 256 bytes EE, low power internal clock
PIC16F88 4K ROM, 368 bytes RAM, 256 bytes EE, low power internal clock AND with 7 channels of 10 bit AD converter
The last device is particularly attractive as is would allow a complete TSP (telephone signal processor) to be produced on the one 20 pin chip. Not bad for a 100 off price of $2.47
If you prefer the 18FXXX core, then the 18F1220 and 18F1320 may be of interest with 2K or 4K of ROM, 256 bytes RAM, 10 bit ADC, power management and will run up to 40MHz.
regards,
Ken Boak