strange problem ! pic18f4550 & pic16f84a serial communication .

[Rob]

Hi,

not sure if your Oscillator is set to the correct frequency. 20MHz; should this not be 48MHz? Are you defining the configs correctly for use with PLL?

For a 20MHz crystal I use these:

    'Config1L
'    Full-speed USB Clock Source Selection: Clock Source from 96MHz PLL/2
'    CPU System Clock Postscaler: Prescaler Divide by 5 for 20MHz Crystal
'    96MHz Prescaler: Divide by 5 (20MHz Input) 
@ __CONFIG _CONFIG1L, _USBDIV_2_1L & _CPUDIV_OSC1_PLL2_1L & _PLLDIV_5_1L

    'Config1H
    'Oscillator: HS oscillator, PLL enabled, HS used by USB
    'Fail-Safe Clock Monitor Enable: Enabled
    'Internal External Switch Over Mode: Disabled
@ __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEM_ON_1H & _IESO_OFF_1H

Cheers

Rob

[amenoera]

thanks for reply , but when i paste this code i get an error .

and am sure i setup it to correct frequency .

error :
overwriting previous address contents (0000) .
symbol not previously defined (_fcmem_on_1h) .

regrads .

[skimask]

error :
overwriting previous address contents (0000) .
symbol not previously defined (_fcmem_on_1h) .

I've seen this before somewhere. Don't remember what the deal was.

Do a search on fcmem and fcmen.
Should fix you up...

EDIT: Found it...
Old versions of MPLAB use FCMEM, new one uses FCMEN

http://www.picbasic.co.uk/forum/show...m+fcmen&page=3
Post #82

[Rob]

thanks for reply , but when i paste this code i get an error .
and am sure i setup it to correct frequency .

Skimask has given you the answer for the error but the frequency will need to be defined as 48MHz when you correct to FCMEN instead of FCMEM. This is because the config settings I have given you set the PIC to run from 48MHz PLL clock source which is generated by the PIC internally but using your 20MHz crystal as the original clock source.

Hope this helps. Let us know how you get on.

Cheers

Rob

[amenoera]

woow , yes you are right .

all i did is :

1 : for this "symbol not previously defined (_fcmem_on_1h) " error , i changed it

to "(_fcmen_on_1h" .

2 : i comment this lines in "18f4550.inc" in my "pbp" folder :

; __CONFIG _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
; __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H

this 2 line is reponsable for this erro "overwriting previous address contents (0000)"

3 : i change "define osc 20" to "48" .

after that , all works fine , and i can now send and recive without any problems .

thanks again .

regards .

[Rob]

Excellent,

glad it's working for you!

Kind regards

Rob