External clock on 16f819 problem.

[tasmod]

Hmm, my post isn't very clear.

I have the software working on a development board. This board uses a 10Mhz Xtal osc as standard.

The board I want to use it on uses an external 10Mhz oscillator source on one pin only OSC1.

I believe I need to set OSCCON=8 to select mode 8 in the oscillator settings. It appears my programmer is defaulting to the 'inc' values.

[Demon]

...The board I want to use it on uses an external 10Mhz oscillator source on one pin only OSC1.
...

Can you give more information about that board?

I've never seen a circuit using only one pin for the oscillator (it doesn't mean it doesn't exist).

Robert

EDIT: Interesting, Pierce and Colpitts oscillators have only one output:
http://ww1.microchip.com/downloads/e...tes/00826a.pdf

...The board I want to use it on uses an external 10Mhz oscillator source on one pin only OSC1....

After glancing through that application note, I'd start by checking just how accurate the oscillator is working.

[Dave]

Robert, Havent you ever ran a PIC from an external oscillator before? You only need 1 pin for the input. That frees up another pin for some external use by the designer.

[Demon]

Robert, Havent you ever ran a PIC from an external oscillator before? ...

Always.

...You only need 1 pin for the input. ...

Not wired like this:



Robert

[Dave]

No Robert, Like this:

[Demon]

Wouldn't that need a CONFIG fuse?

Dave, do you have an example from one of your programs?

Robert

EDIT: These are the available fuses for a 16F819:

_CP_ALL                      EQU     H'1FFF'
_CP_OFF	                     EQU     H'3FFF'
_CCP1_RB2		     EQU     H'3FFF'
_CCP1_RB3                    EQU     H'2FFF'
_DEBUG_OFF                   EQU     H'3FFF'
_DEBUG_ON                    EQU     H'37FF'
_WRT_ENABLE_OFF              EQU     H'3FFF'
_WRT_ENABLE_512              EQU     H'3DFF'
_WRT_ENABLE_1024             EQU     H'3BFF'
_WRT_ENABLE_1536             EQU     H'39FF'
_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'

And these are the default settings (PM and MPASM):

        device  pic16F819, hs_osc, wdt_on, pwrt_on, lvp_off, protect_off
        ...    else
        ...        __config _HS_OSC & _WDT_ON & _PWRTE_ON & _LVP_OFF & _CP_OFF

[tasmod]

To all intents and purposes a clock and oscillator are one and the same.

The answer lies at the end of the fuses list 4th from bottom _EXTCLK needs setting as my programmer defaults to standard inc setting.

This is what I need :

_LVP_OFF & _CP_OFF & _BODEN_ON & _MCLR_OFF & _PWRTE_ON & _WDT_OFF & _EXTCLK & _DEBUG_OFF & _WRT_ENABLE_OFF & _CPD_OFF & _CCP1_RB3

[rsocor01]

Robert, Havent you ever ran a PIC from an external oscillator before? You only need 1 pin for the input.

What you posted is an external clock input, like the title says. That's not really an external oscillator.