Firegod
- 16th March 2007, 21:43
It is my first time using an external oscillator. I am using an 18F4525. I have connected a ABRACON Half Size TTL/HCMOS Clock Oscillator PN/ACH-40-EK to the OSC1 pin (40.0 mHz). The oscillator outputs a saw tooth wave form from 1.8 volts to 3.1 volts.
The clock speed of the 18F4525 appears to be about 400 times too slow. Nothing I do changes to speed. I am also unable to get the Fosc/4 signal out of OSC2 when I configure OSC = EC.
The LED changes state approx every four seconds if I use the code:
DEFINE OSC 40
TRISA.1 = 0
ch1 var PORTA.1
loop:
HIGH ch1
PAUSE 100
LOW ch1
GOTO loop
I have edited my 18F4525.inc file located in my c:\pbp directory to the following:
NOLIST
ifdef PM_USED
LIST
"Error: PM does not support this device. Use MPASM."
NOLIST
else
LIST
LIST p = 18F4525, r = dec, w = -311, f = inhx32
INCLUDE "P18F4525.INC" ; MPASM Header
CONFIG OSC = ECIO6 ; Ext Clock with I/O on RA6
CONFIG IESO = OFF ; Disable Internal External Osc. Switch Over
CONFIG PWRT = OFF ; Disable Power-up Timer:
CONFIG BOREN = OFF ; Disable brownout reset
CONFIG WDT = OFF ; Disable watch dog timer
CONFIG MCLRE = OFF ; MCLR pin disabled; RE3 input pin enabled
CONFIG PBADEN = OFF ;Port B A/D disabled
CONFIG LVP = OFF ;Low voltage ISCP disabled
CONFIG FCMEN = OFF ; Fail-Safe Clock Monitor disabled
NOLIST
endif
LIST
EEPROM_START EQU 0F00000h
BLOCK_SIZE EQU 8
I have also tried:
OSCCON.0 = 0
OSCCON.1 = 0
Do I have the wrong part?
Is my configuration wrong?
Does the wave form from the oscillator need to cross zero?
The clock speed of the 18F4525 appears to be about 400 times too slow. Nothing I do changes to speed. I am also unable to get the Fosc/4 signal out of OSC2 when I configure OSC = EC.
The LED changes state approx every four seconds if I use the code:
DEFINE OSC 40
TRISA.1 = 0
ch1 var PORTA.1
loop:
HIGH ch1
PAUSE 100
LOW ch1
GOTO loop
I have edited my 18F4525.inc file located in my c:\pbp directory to the following:
NOLIST
ifdef PM_USED
LIST
"Error: PM does not support this device. Use MPASM."
NOLIST
else
LIST
LIST p = 18F4525, r = dec, w = -311, f = inhx32
INCLUDE "P18F4525.INC" ; MPASM Header
CONFIG OSC = ECIO6 ; Ext Clock with I/O on RA6
CONFIG IESO = OFF ; Disable Internal External Osc. Switch Over
CONFIG PWRT = OFF ; Disable Power-up Timer:
CONFIG BOREN = OFF ; Disable brownout reset
CONFIG WDT = OFF ; Disable watch dog timer
CONFIG MCLRE = OFF ; MCLR pin disabled; RE3 input pin enabled
CONFIG PBADEN = OFF ;Port B A/D disabled
CONFIG LVP = OFF ;Low voltage ISCP disabled
CONFIG FCMEN = OFF ; Fail-Safe Clock Monitor disabled
NOLIST
endif
LIST
EEPROM_START EQU 0F00000h
BLOCK_SIZE EQU 8
I have also tried:
OSCCON.0 = 0
OSCCON.1 = 0
Do I have the wrong part?
Is my configuration wrong?
Does the wave form from the oscillator need to cross zero?