> > Someone wrote:
> > I use PIC 16F mcus at 20MHz and 18F mcus
> > at 40 MHz, is that good enough?
> Volkan wrote:
>
> It is the measurement of processor speed,
> 16millions instruction per second. As far
> as I know in Pic series clock is divided
> by 4 so 20 MHz means 5mips 40 MHz means
> 8mips. The problem is you need to respond
> serial clock which has a period of around
> 4 micro seconds. They do not use any
> known SPI or I2C serial interface.
Yes - the pics do have a 4 phase clock and
not a lot of pipeline action. So a 40Mhz
pic is only 10 Million instructions per
second.
They do however have an instruction set that
is very suitable for bit-twiddling and
software seriel ports. They where originaly
designed to be a I/O coprocesor for other
CPUs so you can imagine they have good
instrcutions for that.
The "efficient for bit twiddling" instruction
set does NOT make up for the lack of "mips"
in most cases though. So a 40Mhz pic might
have better bit twiddling performance than
other 10 MIPS CPUs but it probably ain't
going to make up for another 60% performance
increase to make it as fast as a 16mips TI-
MPS chip.
Just in the interest of starting a "my MCU
is better than your MCU" holy war - I am
going to mention Atmel AVRs as being a good
choice for 20 mips and an almost completly
orthogonal instruction set :D
(plus they have more sensible names for op-
codes than TI seem to furnish their chips)