Hi >@2010.06.09_14:42:49_+0200
Here's some code which shows this.
#include <stdio.h>
#include <stdlib.h>
#include <avr/io.h>
static void initialise(void)
{
char buf[50];
uint8_t i;
// nonsense code that's not optimised away
for (i=0; i<50; i++) UDR0 = buf[i];
}
int main(void)
{
initialise();
// run tasks
while (1) {
// nonsense code that's not optimised away
do { __asm__ __volatile__ ("nop"); } while (0);
}
}
Built using:
avr-gcc -Os -DF_CPU=14745600UL -mmcu=atmega2561 -c main.c -o main.o
avr-gcc -mmcu=atmega2561 -DF_CPU-14745600UL main.o
-Wl,-Map=out.map,--cref,--debug-stubs -o main.elf
avr-objdump -h -S main.elf > main.lss
Assembly output as follows:
00000112 <main>:
112: df 93 push r29
114: cf 93 push r28
116: cd b7 in r28, 0x3d ; 61
118: de b7 in r29, 0x3e ; 62
11a: e2 97 sbiw r28, 0x32 ; 50
11c: 0f b6 in r0, 0x3f ; 63
11e: f8 94 cli
120: de bf out 0x3e, r29 ; 62
122: 0f be out 0x3f, r0 ; 63
124: cd bf out 0x3d, r28 ; 61
126: fe 01 movw r30, r28
128: 31 96 adiw r30, 0x01 ; 1
12a: 9e 01 movw r18, r28
12c: 2d 5c subi r18, 0xCD ; 205
12e: 3f 4f sbci r19, 0xFF ; 255
130: 81 91 ld r24, Z+
132: 80 93 c6 00 sts 0x00C6, r24
136: e2 17 cp r30, r18
138: f3 07 cpc r31, r19
13a: d1 f7 brne .-12 ; 0x130 <main+0x1e>
13c: 00 00 nop
13e: fe cf rjmp .-4 ; 0x13c <main+0x2a>
Space taken on stack: stack pointer on mega2561 are 0x3d and 0x3e.
--
Cheers,
Dale.
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