Re: PIC18F intermittant reset
- From: "Anthony Fremont" <anyone@xxxxxxxxxx>
- Date: Thu, 19 Jul 2007 20:07:19 -0500
Mook Johnson wrote:
"Anthony Fremont" <anyone@xxxxxxxxxx> wrote in message
news:139uuhsnk4f1m18@xxxxxxxxxxxxxxxxxxxxx
I assume you've tried a different chip just to rule out a bad part. Do
you have the watch dog disabled (WDT)? What about the brown-out
detect (BOD)? If you ran off the end of the program or jumped into
unused code space, a blank chip (at least 16F series) will wrap
around and look allot like a reset.
If it did jump to a blank address space, what whould that do? Assume
the OP code woul be 0x0FF? Reset like action?
On a 16F, the instruction 0x3FFF is "ADDLW 0xFF", on the 18F the instruction
0xFFFF is a "NOP". So yep, it will run until the PC wraps around and that
will likely look like a reset to you.
I have tried different chips and all act the same. The only thing I
cna figure is somewhere in the code an instruction is executing on
the A2D readings or something and causing a invalid condition which
makes the chip reset.
I don't know what conditions would cause the chip to reset though.
The watchdog timer (WDT), a brownout detect (BOD), MCLR assertion, or a
power on reset (POR). That's about it for a 16F. Looks like the 18F4520
adds stack over/underflow and an actual RESET instruction to the list.
That's going to be the only ways (discounting things like static zaps) of
causing an actual device reset.
Since you are using 3.3V, beware of the BOD.
.
- References:
- PIC18F intermittant reset
- From: Mook Johnson
- Re: PIC18F intermittant reset
- From: Anthony Fremont
- Re: PIC18F intermittant reset
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