Microchip PIC Forum: Re: [piclist] Re: 12F675 Startup Problems

Friday, December 7, 2007

Re: [piclist] Re: 12F675 Startup Problems

The OSCCAL calibration byte is programmed into top of memory in the
chip, as long as you don't erase it. Good programmers and programmer
software will read that byte in before erasing the chip and put it back
out when the chip is programmed.

DLC

kg4pid wrote:
> To make it work I had to change the the value that gets moved into
> OSCCAL. Since the serial routine that I used had been around awhile
> I can only assume that the problem is in the Pic oscilator. Don't
> know what to do to fix it though as I don't want to have to
> calibrate each pic chip.
>
> Max
>
> --- In piclist@yahoogroups.com, "kg4pid" <kg4pid@...> wrote:
>
>>I'm using a serial routine on a 12F675 and started by sending out
>
> the
>
>>word "HELLO" over and over. Funny thing is while it's powered on I
>
> get
>
>>nothing out, but the instant I remove power it sends out 10 or 11
>>characters. The filter cap is powering it for that fraction of a
>>second. The circuit is being powered by a 9V battery with a 78L05
>
> to
>
>>regulate it at 5V. My meter reads 4.99v at the pic chip. A logic
>
> probe
>
>>connected to the output blinks the whole time it is powered up
>
> which
>
>>should mean that its sending something. I had to include this bit
>
> of
>
>>code at the very beginning before I got anything at all.
>>call 0x3FF ; Retrieve Factory Calibration
>>BANKSEL OSCCAL ; BANK1
>>movwf OSCCAL
>>
>>Anyone have any ideas as to what might cause a problem like this?
>>
>>Thanks, Max
>>
>
>
>
>
>
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Dennis Clark TTT Enterprises
www.techtoystoday.com
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