16F877 upgrade to 18F4620

[skimask]

thanks for the help,
Have you used the internal oscillator on this chipset? up to 40Mhz according to the datasheet.

The datasheets says it'll run UP TO 40Mhz internally, by using the 4xPLL, meaning the most you can put in externally is 10Mhz.
I've had ONE run at 25Mhz on an external clock (by mistake before I read the datasheet closely), but that's not the norm and most likely won't work for others, not to mention it ran a bit flakey, locked up often, that sort of thing.

EDIT: Ya, what Mr.E said...I really should read first...

[earltyso]

Thanks again for the help!

[Jumper]

I downloaded the pdf file from microchip's webpage and read it.

It said:

Two External Clock modes, up to 40 MHz

These 2 modes are:

9. EC External Clock with FOSC/4 Output
10. ECIO External Clock with I/O on RA6

So it is not possible to use the PLL in these modes but the PIC will run at 40 Mhz if it has a 40 Mhz oscillator connected. I run several 4620 on 40 Mhz, both as 10 Mhz +4*PLL and as pure 40 Mhz circuits.

Also can this be found under absolute maximium ratings:

All devices 15 35 mA -40°C
VDD = 4.2V
FOSC = 40 MHZ
(PRI_RUN,
EC oscillator) <--------- look here!!!
16 35 mA +25°C
16 35 mA +85°C
All devices 21 40 mA -40°C
21 40 mA +25°C VDD = 5.0V
21 40 mA +85°C


So there should be no problem at att to run a 18F4620 with EC or ECIO configuration bits from an external 40 MHz oscillator if Vdd > 4.2V and if it is an industrial rated PIC (figure 26-1) the LF and extended rated PIC has a different behaviour.

/me

[skimask]

I downloaded the pdf file from microchip's webpage and read it.
It said:
Two External Clock modes, up to 40 MHz
These 2 modes are:
9. EC External Clock with FOSC/4 Output
10. ECIO External Clock with I/O on RA6
/me

I'll be.... guess I should have read further into it.
Oh well. Run 10Mhz external gives the option of a sort of clock throttling anyways, switching between the various oscillators, both internal and external. I use it a lot to save battery juice.