16F88 internal clock configuration

[mister_e]

Not quite sure as i didn't see any parts of your code but, if your 8MHZ setting is ok, you also must add DEFINE OSC 8 at the top.. did you?

for the internal setting, see datasheet in the OSCCON. all the setting are there.

in your case for 8MHZ
OSCCON=%01111000

for 4MHZ
OSCCON=%01101000

and so on for the other type of setting

[Tom Gonser]

Much closer.. THANKS!

I now see data on the LCD and on the 4800b Hyperterm screen, but the numbers are incorrect.. and the routines run differently..

Where data was reporting '1009', the text tag is fine, but the actual data is different..... like '3345', etc.

It looks like a timing problem some way?

Would the config bits effect this?

TG

[mister_e]

As we don't have any more info on your current project, it's still hard too see what's wrong with.. BUT at least, since your LCD and your serial communication are working without any kind of garbage display, it's a good sign that your PIC and code are running at the good speed.

If you did some assembler delay or something using TIMERs you must set your prescallers, rates, and delay with the new crystal speed

Did you try with the internal 4MHZ setting???

[Tom Gonser]

Hmmm.. I have tried with:

DEFINE OSC 4 'I want to use 4 mhz?
OSCCON=%01101000

and with setting these to 8Mhz ..

DEFINE OSC 8
OSCCON=%01111000 '8 Mhz

Both work about the same - 'some' plain text comes through, but the code is resetting because I am getting the initialization routine, which does not happen usually.

I am not doing any interrupts or anything, no jumps to assmbly code - pretty straightforward.

I did change the INC files:

changed the "XT_OSC" for "INTRC_OSC_NOCLKOUT" - It looks like this now:

;************************************************* ***************
;* 16F88.INC *
;* *
;* By : Leonard Zerman, Jeff Schmoyer *
;* Notice : Copyright (c) 2003 microEngineering Labs, Inc. *
;* All Rights Reserved *
;* Date : 08/13/03 *
;* Version : 2.45 beta *
;* Notes : *
;************************************************* ***************
; Modified by THG - changed clock settin from XT_OSC
NOLIST
ifdef PM_USED
LIST
include 'M16F88.INC' ; PM header
device pic16F88, INTRC_OSC_NOCLKOUT, wdt_on, pwrt_on, lvp_off, protect_off
XALL
NOLIST
else
LIST
LIST p = 16F88, r = dec, w = -302
INCLUDE "P16F88.INC" ; MPASM Header
__config _CONFIG1, INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _LVP_OFF & _CP_OFF
NOLIST
endif
LIST

The strangest thing is that the program appears to be restarting when it should not. It should be looping through the main routine, but on the F88, it is picking up the initialization routine every few seconds.

scratching head....

[mister_e]

Hehe... i guess i found the problem

Here's all the configuration fuse available for you 16F88

;Configuration Byte 1 Options
_CP_ALL                      EQU     H'1FFF'
_CP_OFF	                     EQU     H'3FFF'
_CCP1_RB0		    		 EQU     H'3FFF'
_CCP1_RB3                    EQU     H'2FFF'
_DEBUG_OFF                   EQU     H'3FFF'
_DEBUG_ON                    EQU     H'37FF'
_WRT_PROTECT_OFF             EQU     H'3FFF'	;No program memory write protection
_WRT_PROTECT_256             EQU     H'3DFF'	;First 256 program memory protected
_WRT_PROTECT_2048            EQU     H'3BFF'	;First 2048 program memory protected
_WRT_PROTECT_ALL             EQU     H'39FF'	;All of program memory protected
_CPD_ON                      EQU     H'3EFF'
_CPD_OFF                     EQU     H'3FFF'
_LVP_ON                      EQU     H'3FFF'
_LVP_OFF                     EQU     H'3F7F'
_BODEN_ON                    EQU     H'3FFF'
_BODEN_OFF                   EQU     H'3FBF'
_MCLR_ON		   		     EQU     H'3FFF'
_MCLR_OFF                    EQU     H'3FDF'
_PWRTE_OFF                   EQU     H'3FFF'
_PWRTE_ON                    EQU     H'3FF7'
_WDT_ON                      EQU     H'3FFF'
_WDT_OFF                     EQU     H'3FFB'
_EXTRC_CLKOUT		    	 EQU     H'3FFF'
_EXTRC_IO		    		 EQU     H'3FFE'
_INTRC_CLKOUT                EQU     H'3FFD'
_INTRC_IO		    		 EQU     H'3FFC'
_EXTCLK			    		 EQU     H'3FEF'
_HS_OSC                      EQU     H'3FEE'
_XT_OSC                      EQU     H'3FED'
_LP_OSC                      EQU     H'3FEC'

;Configuration Byte 2 Options
_IESO_ON                     EQU     H'3FFF'
_IESO_OFF                    EQU     H'3FFD'
_FCMEN_ON                    EQU     H'3FFF'
_FCMEN_OFF                   EQU     H'3FFE'

use _INTRC_IO instead... i'm sure that will work.

[Tom Gonser]

I am using the _INTRC-IO, and also tweaked the serin2 stuff, so I have 'data' coming across all com lines now. Problem is that it is just 'off'..

1. ) It is resetting. I have one routine at the front which only happens on power up. The data from this is showing up off and on.

2.) the math is off. Where a value should sa 4.9volts it reads 3.3. Were a GPS lat should be 47.xxx, it reads 65,511, or some such. Same with all the other values, so I am sure the loops are off.

I made a simpler program that just spewed data to the different com ports - out on RB2, RA0, RA1. This just said "text", #counter - and looped from 1-100.. that worked fine. When I put the full program in, it gives bad data.

I think the original program for the 16F876/a was a 4Mhz program (??).. Does running this at 8 Mhz mess that up? Is there some setting that is needed? Does not seem like there should be....

Thanks a bunch for your assistance - I've never 'ported' from one PIC to another. This program works great on the other one... but we need to be on the F88.. did not know it was going to be so hard.

Tom

[mister_e]

o.k now it seems more a hardware problem than a software problem. be sure your supply line is neat an un-noisy. 10uF tantalum+0.1uF must be place close to your PIC... AS close as you can.

AND be sure your MCLR pin is tie to VCC via resistor.

Enable power-up timer can be great. Also as Melanie previously said it can be interesting to test the 'oscillator frequency is stable bit' before proceed to any of your initialisation process.

look at the a/d register setting(ADCON and others)... i'm sure that they're different from the PIC you used before.