How to create delays in AVR assembly language

Question

Hi i'm new to AVR assembly language so i was trying to get delay function to create 1 ms , 100us, and 1us delays to do that i need to figure out what to replace nop's with below here (mainboard arduino uno r3 ATmega328 Thank you.

"delay_ms%=: nop ; code to replace nop \n"
"delay_100us%=: nop ; code to replace nop \n"
"delay_1us%=: nop ; code to replace nop \n"
" sbiw r30,1 ; decrement ms count (r31:r30)\n"
" brne delay_ms%= ; loop to delay_ms while > 0 \n"
" ret ; return from subroutine \n"

The rest is below.

word millisecs; 
Serial.begin(9600); 
} 
void setup() asm volatile(
" ldi r16,0x3F ; r16 = 00111111\n"
" out 4,r16 ; set pins 8-13 as outputs in DDRB\n" 
::: "r16");
millisecs = 1000; // 1s blink delay
Serial.begin(9600);
}
void loop() 
{
long starttime = millis(); // make a note of the start time
asm volatile(
// jump to "blink" - ie jump around the delay_ms subroutine
" rjmp blink%= ; relative jump to 'blink' \n"
" ldi r16,0x3F ; r16 = 00111111\n"
" out 4,r16 ; set pins 8-13 as outputs in DDRB\n"
::: "r16");
registers used:
r31 - millisecond count (lo byte)
r30 - millisecond count (hi byte)
r17 - 100 microsecond count
r16 - 1 microsecond count
Overall delay (ms) = r30:r31 * r17 * r16
---------------------------------------------------------------------*/
"delay_ms%=: nop ; code to replace nop \n"
"delay_100us%=: nop ; code to replace nop \n"
"delay_1us%=: nop ; code to replace nop \n"
" sbiw r30,1 ; decrement ms count (r31:r30)\n"
" brne delay_ms%= ; loop to delay_ms while > 0 \n"
" ret ; return from subroutine \n"

• Chris Stratton: This is a pure programming question and probably should have remained on stackoverflow, rather than been migrated here.
• user1653: its atmega328 so 16mhz but how many clock cycles would that be 16000 for 1 millisecond?

Answer 1

AVR LibC already has macros that do this, provided F_CPU is set correctly.

// Note: The Arduino IDE gets the value for F_CPU from boards.txt
#define F_CPU xxxxxxxxxx
#include <util/delay.h>
 ...
_delay_ms(1);
_delay_us(100);
_delay_us(1);