PIC181220/1320 40Mhz

NikkiC · Guest

Hi,

I've have attempted to use the H4 mode to run PIC18F1220/1320 at 40 Mhz. The clock is totally unstable. I've tried a few chips. I've never had a problem with PIC18F252/452.

I'm using PCH 3.170. Does anyone know if this is a problem specific to earlier versions of the compiler? I'm trying to rule out a hardware issue.

Thanks,

Nikki

|Raph| · Guest

We are using CCS v3.188 here and we tried it on many 18LF1320 with no success.

Neutone · Joined: 08 Sep 2003 Posts: 839 Location: Houston

To run at 40Mhz the supply voltage must be greater than 4.2V. Also to change from the HS to 4xHS you have to cycly power after programming. Nikki I assume that your 10Mhz crystle works without the 4xHS setting?

Guest · Posted: Thu Apr 08, 2004 12:37 pm

Yes, it is definitely running at 5V.

The cycling off power goes without saying as I'm manually plugging the PIC into a Warp13 programmer and then back into my development board by hand.

All the PICs work with no problem at 10Mhz with
#use delay(clock=10000000)
#fuses HS, BORV20, MCLR,NOLVP,NOWDT,NOBROWNOUT

and then fail to run with any stability with
#use delay(clock=40000000)
#fuses H4, BORV20, MCLR,NOLVP,NOWDT,NOBROWNOUT

The clock fluctuates between 10Mhz and 40Mhz.

Nikki

C-H Wu · Guest

20 MHz ... ok.
40 MHz with 10 MHz X'tal and H4PLL, never success, with chip date code up to 0404 (4th week of 2004)

I believe it is a silicon bug.

Internal 8 MHz ... ok ... this is good, cheers.

Guest · Posted: Fri Apr 09, 2004 1:29 am

Do you have a resistor series with crystal? Use 100-470 Ohm.