12f675 probably a silly question

[Meriachee]

Hi folks,

I've been using 16f819s for a while now and needed a smaller package for a space restricted installation, so I got a handfull of 12f675s.

I'm using PBP and the 4.x melabs programmer and putting a 4k7 to vdd for MCLR. Nothing else is being set specifically, except of course intosc, watchdog enabled, brownout enabled and powerup enabled.

The chip will not start. All I did to test it was put a 220 to a led from GP5, pretty standard test.

Checked voltages and led wiring and everything is as it should be.

Is there startup files that need to be included with this chip?

help?

Gary

[Kees Reedijk]

I tried this code and that should work:

'flash that led!
@ device pic12F675, intrc_osc, wdt_on, pwrt_on, mclr_off, protect_off

ANSEL = 0
CMCON = 7
TRISIO = 0
GPIO = 0

LED VAR GPIO.5

loop:
Toggle led
Pause 100
goto loop

End

[Darrel Taylor]

Hi Gary,

It's hard to tell without the code you're using, but here's something to look at.

INTOSC, is the same as INTRC_OSC_CLKOUT. Which means that FOSC/4 (1mhz) will be put out on GP4. If you have an o-scope, you can look for this signal to see if the processor is running or not.

If there is anything attached to GP4, it could also cause the chip to reset from over-current.

>> I'm using PBP and the 4.x melabs programmer

Is that 4.1? If so, look at the Code window in meProg.exe. (View | Memory)
Open the HEX file and press the program button. Now look at location 0000 in the code window. Has it changed?

There's a bug in that version that sometimes causes the first word to change to 0000h, which makes the program not run. If that's the case, you can download the 4.2 beta from the melabs website.

Here's a simple blink program for the 12F675...

@  device  pic12F675, intrc_osc_noclkout, wdt_off, mclr_off, protect_off

CMCON = 7
ANSEL = 0

Main:
    TOGGLE GPIO.5
    pause 500
goto Main

<br>

ADDED: Kees, intrc_osc isn't valid for a 12F675

[Meriachee]

Thanks guys. It's always something stuipd, and this time is no exception. If you want a GPIO port to be a port, you have to define it as a GPIO.x not portb.x as I am obviously far too accustomed to. Ports were not defined as evidenced by the floating voltage.

She's avery pretty blinking led!

Thanks again.
Gary

[mister_e]

PORTB is already define but leads you to Register addr 6... wich is unimplemented on this PIC

PORTA is assign to register addr 5, wich is GPIO

in the above, if you replace GPIO by PORTA, it will work.

Not a good practice but...

[Darrel Taylor]

Hmm, never realized PORTA and B were in there.
That's odd about PORTB pointing to an unimplemented register. It keeps the compiler from finding problems like what Gary had.

12F675 How do I address thee, let me count the ways.<pre>PORT TRIS<br>-------------<br>GPIO TRISIO<br>PORTA TRISA<br>PORTL TRISL<br>PORTH TRISH</pre>or you can use PIN numbers...<pre>HIGH 5 ; will set GPIO.5 to OUTPUT HIGH<br>or <br>TOGGLE 5</pre>Although a bit strange...

<pre>TOGGLE 13 ; will also toggle GPIO.5</pre>
OK, so that's only 6, who's got number 7 ??

[mister_e]

PORT TRIS
-------------
GPIO TRISIO
PORTA TRISA ' errr... PORTB?
PORTL TRISL
PORTH TRISH

But... for #7, if there's .... euhhh