Fastest PIC18 available

[carl]

Hi there,

Can anybody please explain to me my options regarding my choice of fastest PIC18 available.

After looking at the parameter search at Micrchip, I am slightly confused.

Usually the max CPU speed is set by an external oscillator (I can find 64Mhz), and the CPU speed is divided by four to give you your clock speed.

But I have found ones that use PLL to increase the speed from the external oscillator - would this give a faster clock speed??

My overall aim is to get the fastest PIC18 clock speed available.

Thanks
Carl

[n-squared]

Hi
Microchip allows you to use the internal RC or an external crystal up to 16MHz, then use the internal PLL to multiply the frequency by 4, and THEN the circuitry DIVIDES it back to 16MHz for a 16MIPS cpu. That is the fastest you can achieve with PIC18 chips.

For higher speed you need to look at PIC24 or dsPIC3x chips.

BR
NN
_________________
Every solution has a problem.

[temtronic]

Also speed isn't everything ! It does allow sloppy code to run(Windows..applications) while good,tight coding can get the job done better.
My current laptop has kbd,lcd,word processor,rs232,LPT,bar code reader,modem,paging,etc. with only 32KB of RAM,32KB ROM,4MHz xtal.
My point is that code rather than speed is better.

[carl]

Hi there,
Thanks for your replies.

N-Squared - thanks for the explanation - understand it now. But I'm sure I have seen somewhere a 96Mhz PLL - which would give a clock of 24Mhz.

Are you sure of the 16Mhz Clock being the fastest??

Temtronik - Understand and agree, although as usual it all depends on the application, and I think the new application will have to be fast regardless of the coding.

Thanks
Carl

[Ttelmah]

The 96MHz PLL, is inside _USB_ PIC's. Not used directly to feed the CPU, but only via a divider (usually /2 to give 48Mhz operation).
A lot of the PIC24 chips will go much faster, but 64Mhz, is about the fastest current PIC18. 16MIPS.

Best Wishes

[carl]

OK thanks All

[carl]

Hmmm...

All the 64Mhz pic options (production types) all have a 'k' in the part, and I cannot find any of these parts supported in the my PCWH compiler 4.038.

Also the parts are not included in the devices file on my computer, and not all are included in my MPLAB version 8.10.00.00.

Ideally I would like one with high I/O count also (64).

So how would I go about resolving this issue??

Cheers
Carl

[temtronic]

You'll have to upgrade your compiler to be able to program the 'newer' PICs.

Sign of the times...they're making versions faster than we can figure out what to do with them !

With your requirement for fast speed and high pin count, perhaps your application can be split into 2 or 3 smaller PICs( distributed processing) ?

[ckielstra]