75 lines
2.1 KiB
C
75 lines
2.1 KiB
C
/**
|
|
* Copyright (C) 2009 Ubixum, Inc.
|
|
*
|
|
* This library is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* This library is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this library; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
**/
|
|
|
|
#include <fx2regs.h>
|
|
#include <fx2macros.h>
|
|
#include <delay.h>
|
|
|
|
void
|
|
delay(WORD millis)
|
|
{
|
|
/**
|
|
* It takes 12 crystal pulses to make 1 machine cycle (8051.com)
|
|
* ez-usb trm 1.13
|
|
* 83.3 ns at 48mhz per instruction cycle
|
|
* (assume 166.6ns at 24mhz)
|
|
* (assume 333.3ns at 12mhz)
|
|
* ez-usb trm 12.1
|
|
* Includes the cycles for each instruction
|
|
**/
|
|
WORD loop_count;
|
|
volatile WORD count; // NOTE perhaps use different solutions w/ out volatile
|
|
|
|
|
|
// set count to the number of times we need to
|
|
// go around a loop for 1 millisecond
|
|
|
|
// then do that loop millis times. (1000 us=1ms)
|
|
|
|
// 48mhz: 1000 us / (17 cycles * 83.3 ns / cycle / 1000 ns/us) = 706
|
|
// 24mhz: 353
|
|
// 12mhz: 177
|
|
// recalculate if the number of cycles changes
|
|
// like if you change the loop below
|
|
loop_count = CPUFREQ == CLK_12M ? 177 : CPUFREQ == CLK_24M ? 353 : 706;
|
|
|
|
// sdcc generated assembly
|
|
/* cycles code
|
|
; delay.c:31: do {
|
|
00101$:
|
|
; delay.c:32: } while ( --count );
|
|
2 dec _delay_count_1_1
|
|
2 mov a,#0xff
|
|
4 cjne a,_delay_count_1_1,00121$
|
|
2 dec (_delay_count_1_1 + 1)
|
|
00121$:
|
|
2 mov a,_delay_count_1_1
|
|
2 orl a,(_delay_count_1_1 + 1)
|
|
3 jnz 00101$
|
|
|
|
Total 17
|
|
*/
|
|
|
|
do {
|
|
count = loop_count;
|
|
do {
|
|
} while (--count);
|
|
} while (--millis);
|
|
|
|
}
|