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Re: [avr-gcc-list] Align Data and RAM Gaps

From: Erik Christiansen
Subject: Re: [avr-gcc-list] Align Data and RAM Gaps
Date: Sat, 9 Aug 2014 18:39:26 +1000
User-agent: Mutt/1.5.21+145 (2a1c5d3dd72e) (2012-12-30)

On 09.08.14 18:18, Erik Christiansen wrote:
>    ldiw  Z,buf

What, that's not an avr mnemonic? It is if you have this in a header

; Data Pointer (or any word value) initialisation of a register pair.
; Usage: ldiw  Y,some_data
;        ld    r16,Y          ; OR lpm r16,Y if some_data is in flash.
                              ; Avoids need for manual endianness perfection.
   .macro ldiw reg,addr
   ldi   \reg,lo8(\addr)
   ldi   (\reg + 1),hi8(\addr)

And for completeness:

; Program Pointer (word address) initialisation of a register pair.
; Usage: pptr  Z,program_address
;        icall

   .macro pptr reg, addr
   ldi   \reg, pm_lo8(\addr)           ; Word addressed program memory.
   ldi   (\reg + 1), pm_hi8(\addr)

There's no reason why we should do word operations by hand, especially
with that lo8/pm_lo8 guff to increase the likelihood of human error.


Programs must be written for people to read, and only incidentally for
machines to execute.                            - Abelson and Sussman

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