[sdiy] New 16F18xx enhanced mid range PICs

[Tom Wiltshire]

Hi All,

I've been playing with some of the new Microchip 16F PICs. They're identifiable because their part numbers all start 16F1xxx.
The two chips I've looked at specifically are the 16F1824 and the 16F1847.

There are various fairly minor changes, but overall they make significant improvements to both speed and memory usage.

1) Low voltage versions - You can get the chip in an LV version to run on 3.3V if you want
2) 32MHz top speed - a big boost from the previous 20MHz, more than 50% faster in raw power terms.
3) Extra instructions - many of these help shorten the sequences required for common tasks. This saves both program memory and processor cycles.
For example: ADDWFC - Finally, an "add with carry" instruction!! This turns a 24+24-bit addition from a 10 instruction sequence into a 6 instruction sequence.
Also included are better handling of indirection registers with pre/post inc/decrement and more versatile bit-shifting instructions,
4) Two indirection registers. This also speeds things up since you don't have to set them up so often. You can use one for writing samples to memory and one for reading them out, for example.
5) Shadow registers for automatic context saving for interrupt routines. This is another simple thing, but a big improvement. Saving and restoring context can easily use up twenty instructions in an interrupt routine. This saves all that work, shortening interrupts significantly.
6) Lots of extra peripherals for no more money - more ADC, more PWM, more SPI, more UARTs, etc etc. This is useful, but not really that important. The range of previous chips was so wide, you could always find one with all the things you need.

In short, I'm impressed with the new chips. The additions are thoughtful - someone has looked at what people really use and added a few key details that make life much easier/faster, without implying great changes.

If there'd been a "multiply" as well, it might have been the killer chip for a quid.

Tom