18f4550 running slow?

[Darrel Taylor]

melabs has replied (yesterday), maybe you didn't get the email.

And nothing you've reported "Points to" DEFINE OSC.
What it does suggest is a problem with your oscillator.

If IESO is 0 then the code fails to run totally. When it's set, the whole thing is much slower than expected.

IESO is the "Internal/External Oscillator Switchover bit".
Meaning that on power-up it starts running on the internal oscillator, then when the external oscillator is running and stable it switches over to that.
If the external oscillator is not running properly, it never switches over.

The default (power-on) frequency of the internal oscillator is 1 Mhz, so with DEFINE OSC 20 it will take 20 seconds to execute a PAUSE 1000. And everything else will run at 1/20th speed too.

You say that you are swapping between a 2550 and 4550.
The pins are different. Are you sure you have the crystal and caps on the correct pins after swapping.
On the 2550, it's pins 9 and 10. On the 4550 it's pins 13 and 14.

The 2550 only has one VDD pin and the 4550 has two. Are you connecting both VDD's.

[Demon]

Try this:

@   __CONFIG    _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@   __CONFIG    _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H
@   __CONFIG    _CONFIG2L, _PWRT_OFF_2L & _BOR_ON_2L & _BORV_1_2L & _VREGEN_ON_2L
@   __CONFIG    _CONFIG2H, _WDT_OFF_2H
@   __CONFIG    _CONFIG3H, _CCP2MX_OFF_3H & _PBADEN_OFF_3H & _LPT1OSC_OFF_3H & _MCLRE_ON_3H
@   __CONFIG    _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _ICPRT_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L

DEFINE OSC 48

TRISA = %00000000
TRISB = %00000000
TRISC = %00000000
TRISD = %00000000
TRISE = %00000000

ADCON1 = %00001111

Led var PORTC.2

Loopthis:
  toggle Led
  pause 500
  goto LoopThis

END

It blinks at 1 second intervals on my 18F4550 using external 20 MHz oscillator.

Robert

[Giulio]

I stand corrected. MELabs did reply [thanks Darrel], and the mail somehow found its way into my spam folder?

By way of an apology, sorry if it sounded like I was complaining. I most certainly was not. Their support, when I've contacted them in the past, has been immediate, and first rate. I only mentioned it above in case anybody asked if I'd contacted them.

Darrel sent the following fuse settings, which worked! Thought I'd tried every combination, but obviously had not. Thank you Darrel !

G

p.s. Thanks too, to Demon, for your settings example, and everybody else that took time out to help a confused hobbyist!

#CONFIG
CONFIG PLLDIV = 5 ; Divide by 5 (20 MHz oscillator input)
CONFIG CPUDIV = OSC1_PLL2 ; [Primary Oscillator Src: /1][96 MHz PLL Src: /2]
CONFIG USBDIV = 2 ; USB clock source comes from the 96 MHz PLL divided by 2
CONFIG FOSC = HS ; HS oscillator, PLL enabled (HSPLL)
CONFIG FCMEN = OFF ; Fail-Safe Clock Monitor disabled
CONFIG IESO = OFF ; Oscillator Switchover mode disabled
CONFIG PWRT = OFF ; PWRT disabled
CONFIG BOR = ON ; Brown-out Reset enabled in hardware only (SBOREN is disabled)
CONFIG BORV = 3 ; Minimum setting
CONFIG VREGEN = ON ; USB voltage regulator enabled
CONFIG WDT = ON ; WDT enabled
CONFIG WDTPS = 512 ; 1:512
CONFIG CCP2MX = ON ; CCP2 input/output is multiplexed with RC1
CONFIG PBADEN = OFF ; PORTB<4:0> pins are configured as digital I/O on Reset
CONFIG LPT1OSC = OFF ; Timer1 configured for higher power operation
CONFIG MCLRE = ON ; MCLR pin enabled; RE3 input pin disabled
CONFIG STVREN = ON ; Stack full/underflow will cause Reset
CONFIG LVP = OFF ; Single-Supply ICSP disabled
CONFIG ICPRT = OFF ; ICPORT disabled
CONFIG XINST = OFF ; Instruction set extension and Indexed Addressing mode disabled (Legacy mode)
CONFIG DEBUG = OFF ; Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins
#ENDCONFIG

[J. Mark Wolf]

Which fuse made the difference to your problem?

[Giulio]

Well, that's poor form on my behalf, as I'm not sure!

I was changing them in mplab, trying every combination [or so I though], but not keeping track, which is a 'random' approach to solving a problem, and nothing to be proud of.

My frustration got the better of me. I shall remove the settings that Darrel sent me, and have a look at the default, and see what happens, as I should be documenting this, for my own reference...

G