Thanks for the input Olin.  That's quite a set of macros you have.  I'll
have to remember those and after I get a foot or two on the ground, I may
come back to them.  Right now only have a toe or two on the ground re PICs.

One answer always seems to raise more questions.  Your macro's use
IF/Endifs.  Does MPLAB and most assemblers support them?  I'll go check out
MPLAB.  I just realized the other day that the 12c671 does not have decision
making commands other than the btfsc, btfss, decfsz and incfsz instructions.

Thanks, Jess

-----Original Message-----
From: Olin Lathrop <olin_piclist@EMBEDINC.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Monday, March 05, 2001 9:07 AM
Subject: Re: [PIC]: 12c671 - GPIO vs TRIS Reg


>> Bob, the documentation indicates the GPIO/TRIS registers are at register
>> memory locations 0x05/0x85 and therefore it seems the disassembler should
>> know which register is being addressed.
>
>No, because only the low 7 bits of the address are encoded into the
>instruction.  The upper two bits come from the bank bits.  The disassembler
>can't always know the runtime value of the bank bits, and therefore can't
>tell whether GPIO or TRISIO was addressed.  If in doubt, it reports the
name
>of the register in bank 0.
>
>> So, when coding in assembly, which register name should one use - the
>> register name matching the Bank or is it sufficient to use either name
and
>> preselect the correct Bank?
>
>Always always always use the name of the intended register!  Just because
>using a different name causes the same instruction to be generated doesn't
>make it right.  Imagine someone (or maybe you) trying to figure out in
three
>years what you intended.  Not only might that change from one PIC to
>another, but using an alias register name is like writing deliberately
>misleading comments.
>
>By the way, I deal with this register banking issue by using macros that
>switch banks for me only when needed.  For example, my code might look like
>this:
>
>come_from_someplace unbank   ;clear bank setting assumptions
>     dbankif  trisio         ;set banks for access to TRISIO
>     movlw    12             ;load some value into TRISIO
>     movwf    trisio
>
>     dbankif  gpio           ;change banks as needed to access GPIO
>     movlw    34             ;load some other value into GPIO
>     movwf    gpio
>
>You are free to use my bank switching macros and lots of other stuff.  Go
to
>http://www.embedinc.com/pic and see file STD.INS.ASPIC.
>
>
>*****************************************************************
>Olin Lathrop, embedded systems consultant in Devens Massachusetts
>(978) 772-3129, olin@embedinc.com, http://www.embedinc.com
>

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