Oscillator/Hserout woes

[ScaleRobotics]

Having got the define correct. (define osc 4 ....4Mhz)

The OSCCON still needs setting? (bear with me here - I seldom change this stuff.....if OSCCON still needs setting what's the purpose of the DEFINE command?)

I tried getting the interal oscillator presented on the associated IO pins (to see if I could scop them - failed! IS there something unique about the clock that makes it invisible? lol)

I tried a whole heap of permutations - the Hserout settings I posted were derived from Mr E's calculator.

No, you were correct, it defaults to 4 mhz, and should not need to be set, unless you want to try 8 mhz. Which, maybe you should, just for fun. But try what Henrik suggested with verifying your osc speed by toggling an led, and see what you get, just to be sure.

[HenrikOlsson]

Hi,
DEFINE OSC 4 doesn't do anything with the PICs registers or config "fuses". It simply tells the compiler that you are intending to run the chip at 4Mhz so it knows how to calculate the correct amount of cycles for your PAUSE 250 etc.

The internal oscillator on the '690 is fixed* at 8Mhz but the postscaler (controlled by bits 4, 5 and 6 in the OSCCON register) defaults to a divide by 2 ratio so you end up with 4Mhz as the default. So really, it should be running at 4Mhz.

* The "fixed" 8Mhz oscillator can be tuned by changing the OSCTUNE register.

When you tried to get the CLKOUT to work, did you set the pin to output? (TRISA.4 = 0)

/Henrik.

EDIT: Running at 4Mhz you should see a 1Mhz signal on the CLKOUT pin.

[HankMcSpank]

Hi,
DEFINE OSC 4 doesn't do anything with the PICs registers or config "fuses". It simply tells the compiler that you are intending to run the chip at 4Mhz so it knows how to calculate the correct amount of cycles for your PAUSE 250 etc.

The internal oscillator on the '690 is fixed* at 8Mhz but the postscaler (controlled by bits 4, 5 and 6 in the OSCCON register) defaults to a divide by 2 ratio so you end up with 4Mhz as the default. So really, it should be running at 4Mhz.

* The "fixed" 8Mhz oscillator can be tuned by changing the OSCTUNE register.

When you tried to get the CLKOUT to work, did you set the pin to output? (TRISA.4 = 0)

/Henrik.

EDIT: Running at 4Mhz you should see a 1Mhz signal on the CLKOUT pin.

Great stuff Henrik - like I say, in the end I went back to 20Mhz (& all the associated pin rejigging that entails from having to put back in the an external resonator!)...I don't have the heart or inner strength to now 'rejg' my 'rejig' so to speak ......but I *will* revisit this with the advice/knowledge gained here (I'd dearly love to see some form of clock coming out of the pesky pins - if for no other reason to establish that the PIC isn't holding a grudge against me!)

A hearty thanks!

[cncmachineguy]

Hey Hank, when you do have the heart to re-visit this, use the int_osc clk_out fuse instead of no clk out. This should put the clock on whatever pin it says. As for rejigging pins, can you just pull your resonator to test between internal and external?