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Re: [avr-gcc-list] compiler not generating IO

From: Joerg Wunsch
Subject: Re: [avr-gcc-list] compiler not generating IO
Date: Thu, 26 Jan 2006 21:24:17 +0100 (MET)

"developer2112 (sent by Nabble.com)" <address@hidden> wrote:

> I get in my listing:

>       UDR = 'A';
>  272: 81 e4           ldi     r24, 0x41       ; 65
>  274: 80 93 2c 00     sts     0x002C, r24

> clearly I am not getting an "out" instruction, what gives?

It will work anyway, only not as effective.  Memory-mapped IO (MMIO)
is the only method where access to the entire set of IO registers on
the AVR can be guaranteed for all devices.

If you turn on optimization, the optimizer will recognize that
situation, and turn that into an "out 0x0c, r24" instruction.

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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