16F876 : settings for 40Mhz

[mister_e]

That's strange. I'm not 100% of what i say but, looks like your programmer don't program the configuration bits for your device.

What's happening if you use a 20 MHZ oscillator and use HS mode???

what about now if you use a 4mhz and and use XT mode???

[Melanie]

Whether you set the config bits in your program or not, you should be capable of setting those bits manually prior to burning the PIC. If your programmer is incapable of doing that, you may need a sortware update for it, or alternatively you might need a better programmer.

[mister_e]

that's for sure Melanie. But i think you can setup Melabs programmer to write configuration bits or not... i'm really not sure of what i say. Maybe some EPIC user or Bruce can second this ?

[mischl]

first of all, thanks to steve and melanie for their feedback and help.
unfortunalety is doesn't work better.

i have this versions :
MicroCode Studio Plus 2.1.07
PicBasic Pro 2.44
MPASM 3.90 (updated today from 3.50)
melabs Serial Programmer 3.13 (updated today from 3.10)
firmware of the programmer 3.5 (updated today from 3.2)

my code is this :

@ __CONFIG _CONFIG1H, _OSCS_OFF_1H & _HSPLL_OSC_1H

DEFINE OSC 40

led var porta.0

init:
clear
TRISA = %00000000
PORTA = 0


main:
high led
pause 1000
low led
pause 1000

GOTO main

END

in the 18f242.inc file of the pbp root, i set line 20 as follow :
; __CONFIG _CONFIG1H, _OSCS_OFF_1H & _XT_OSC_1H

assembled with MPASM 3.90, getting no errors and no warnings. nothing.

problem : if i set the osc to 10, it works fine. when i set the osc to 40,
it works 4 times slower. (i work with a 10 mhz at a 18f242 and capacitors
with 22pf). in the melabs settings i test hs as osc as well as the hspll.
both settings have the same effect.

many thanks for any comment and idea...

[mister_e]

It really looks like your programmer don't set the configuration fuses...

i don't have any 18F252, but this one is tested with a 18F452

@ __CONFIG _CONFIG1H, _OSCS_OFF_1H & _HSPLL_OSC_1H
    ' Oscillator switch OFF
    ' Use HSPLL (fosc X 4) oscillator  (10mhz here)
    '
@ __CONFIG _CONFIG2L, _BOR_ON_2L & _PWRT_ON_2L & _BORV_45_2L
    ' Brown out reset ON @ 4.5Volts
    ' Power-up timer ON
    '
@ __CONFIG _CONFIG2H, _WDT_ON_2H 
    ' Watch dog timer ON
    '
@ __CONFIG _CONFIG4L, _STVR_ON_4L & _LVP_OFF_4L & _DEBUG_OFF_4L
    ' Stack over/underflow ON
    ' Low Voltage programming OFF
    ' Background debugger OFF
    
Define OSC 40
Start:
      Toggle PORTC.3
      pauseus 100
      goto start

if you change the DEFINE OSC 40 to DEFINE OSC 10 you'll get 25uSec pulses. So PLL is working very well.

Look into your Melabs programmer setings, must have a place to configure programmer options.

If you can't find something like that, send an e-mail to BRUCE from Reynolds Electronics. [email protected] For sure he know the solution for that.

[mischl]

steve, thanks a lot for the example. this is working very well!

after that my own example works too. unfortunalety i don't know why... i think it was a configuration at the melabs programmer.

once again : thanks all for the support

[mister_e]

mischl

great to know it's working now.

Have fun!

[Bruce]

With the melabs serial programmer make sure you have these two
menu options selected.

Update Configuration From File
Reread File Before Programming

This makes sure you are always getting the latest version of the .hex
file & whatever config word changes you make programmed into the
target.

Also, I recommend inserting "every" config word option the target has.
This way there is no doubt how each option is configured.

With all of the advanced configuration options the 18F series has, It's in
your best interest to know exactly how every option is set. Accepting a
default un-programmed state may cause you problems.

For the 18F series I comment out every default setting in the PBP device
header file, and insert my own config fuse settings in my source.