At 09:43 PM 11/3/99 -0200, roberto1@MAILBR.COM.BR wrote:
>I know its basic, but have your CORRECTLY set the ADCON register? Last
>month I was developing code for '877 and I reached your same problem. It
>was solved changing the ADCON register.

ADCON1 = 0x0F;

which by my read sets the pins as not AD.

I also ran into this at first, but that was weeks and weeks ago.
This is the first thing I checked.  Good suggestion though.

>
>Another thing: When you execute an toggle routine or command, the pic
>reads the pin contents, then togle a bit and shifts out it again to the
>pin, so, depending on your hardware (an led drawing a lot of current for
>example), when the pic reads the pin, the "hi" (an 1) voltage on it is
>below, let's say 2.5v; so the read is interpreted as a low rather then a
>high. If it happens, the real behavior is that the pin don't toggle. It
>also happened to me last month.
>

It is definitely not this, as I pulled it completely out of the circuit.

I'm beginning to suspect that perhaps my programmer is bad.
It has been getting flaky verifies lately.  I have 4 chips on carriers so I
don't think it is bum chips.
I will be investigating further, and let you know how it comes out.
Thanks for the suggestions.

-Erik Reikes

>If it helps, reply so I may track this "interesting" behavior.
>
>see you,
>             Beto.
>
>
>
>
>______________
>I believe I've just found a really nasty hardware bug in the 16F876.  I
>figure I would tell you guys first then figure out who at MChip to give
>a
>piece of my mind.
>
>Here's the scenario : I'm using pin 0 of port A to wakeup an external
>device.  This involves toggling the pin.  If only pin 0 is written to, a
>0
>never comes out on the port.  To get it to write something another pin
>on
>port A must also be written to.
>
>My bare bones software test cases are :
>1: xor pin 0 with 1
>2: delay
>
>In this case pin 0 stays a 1, constantly.  If I change it to :
>
>1: xor pin 0 with 1
>2: delay
>3: write a 1 to pin 1,2,3 or 5;
>4: write a 0 to pin 1,2,3, or 5;
>
>Then it works.  Otherwise nix.  It operates in exactly the same manner
>with
>bsf and bcf on that particular pin.  I didn't see anything in the errata
>on
>this.  I'm more than a bit irritated.  If someone can show me how this
>is a
>bug on my part I'd be grateful (as well as surprised).
>
>Here's the source for working :
>
>m015    MOVLW .1
>00F0 1283  0529         BCF   0x03,RP0
>00F1 1303  0530         BCF   0x03,RP1
>00F2 0685  0531         XORWF PORTA,1
>00F3 0000  0533         NOP
>00F4 0000  0535         NOP
>00F5 0000  0537         NOP
>00F6 0000  0539         NOP
>00F7 0000  0541         NOP
>00F8 1685  0544         BSF   PORTA,5
>00F9 1285  0546         BCF   PORTA,5
>00FA 28EF  0549         GOTO  m015
>
>And for not working :
>m015    MOVLW .1
>00F0 1283  0529         BCF   0x03,RP0
>00F1 1303  0530         BCF   0x03,RP1
>00F2 0685  0531         XORWF PORTA,1
>00F3 0000  0533         NOP
>00F4 0000  0535         NOP
>00F5 0000  0537         NOP
>00F6 0000  0539         NOP
>00F7 0000  0541         NOP
>00F8 28EF  0547         GOTO  m015
>
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