myke predko wrote:

> What you've discovered is a part of the low-end PICmicro MCU architecture
> that *everybody* seems to learn the hard way.  In my datasheet, Bit 7 is
> marked as always being "1" on power up and different processor resets - it
> doesn't indicate that it can never be reset.


I didn't care what value it was at reset, because
I explicitly cleared it in software.
The fact that you CAN'T EVER clear it just happens
to be omitted from the datasheet. If anything
deserves a datasheet warning than that does.
So what happened to the Microchip convention that
unused bits read as zeros???


> ALL low-end PICmicro MCUs will always have the MSB or more MSBs set in the
> FSR at all times, depending on how many register banks are built into the
> device.  This means that the PIC12C50x, PIC16C505, PIC16C5x will all have
> one or more FSR bits always set.
>
> But, the PIC12C67x, PIC16C55x are mid-range architected parts and the FSR
> can have all its bits reset to zero.

> Also make sure you mark the PIC12C50x datasheets as well.


Thanks Myke for the info!! My code was refined and
tested on a number of PICs before loading it into the
16c505. I have marked my datasheets as you suggested.

Adding insult to injury the 16c505 datasheet tells
me "the FSR is a 5 bit register" when in fact it is
a 7 bit register. As someone that spends a lot of time
reading the datasheet when coding new projects I am
rather annoyed that my code was perfect and tested on
a few other PICs and their shoddy documentation cost
me about 10 hours chasing a hardware fault that didn't
exist. Which Microchip address do I send the bill to??
-Roman

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