Hello,

PIC newbie here. I have a couple of questions that have come up over the
past month or so. Neither one is a burning issue, I'd just like to know
the answers, or at least collect a few opinions.

First, refer to the documentation for the RRF and RLF instructions in
MicroChip's Mid-Range MCU manual. I have a question about the contents
of the W register after either of these instructions are executed. The
examples (pages 29-36 and 29-37) show that the contents of W are not
defined prior to executing the instruction, but then they show that W
contains 0x17 after execution. The W reg is not the destination for the
instruction, which is given as RRF INDF,1. The bit-shifted value ends up
in the register whose pointer is in FSR, just as I expect. What I do not
expect or understand is why W would contain a value that doesn't have
any obvious relationship to the contents of the destination register.

I understand the rest of the "Example 2" code just fine - the contents
of the target register and the carry bit are just what I expect. How
does W get set to 0x17? Or does it? I wonder if that is just an
arbitrary example. If so, it is confusing. 

Second, I'm wondering just how much use most programmers make of the
assembler directives. There are a LOT of directives available, yet when
I look at other folk's source code it seems that only a very few
directives ever actually show up in the code. The #include, EQU, and a
few others are very common, as is using $ to refer to the PC. That seems
about it. For example, I'd expect to see more use of DA, DT, BANKISEL,
and BANKSEL. Are there non-obvious drawbacks to using the MPASM
directives? 

Thanks,
   Glenn Minch

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