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1 | /** | |
2 | * Copyright (C) 2009 Ubixum, Inc. | |
3 | * | |
4 | * This library is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU Lesser General Public | |
6 | * License as published by the Free Software Foundation; either | |
7 | * version 2.1 of the License, or (at your option) any later version. | |
8 | * | |
9 | * This library is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * Lesser General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU Lesser General Public | |
15 | * License along with this library; if not, write to the Free Software | |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
17 | **/ | |
18 | ||
19 | #include <fx2regs.h> | |
20 | #include <fx2macros.h> | |
21 | #include <delay.h> | |
22 | ||
23 | void delay(WORD millis) { | |
24 | /** | |
25 | * It takes 12 crystal pulses to make 1 machine cycle (8051.com) | |
26 | * ez-usb trm 1.13 | |
27 | * 83.3 ns at 48mhz per instruction cycle | |
28 | * (assume 166.6ns at 24mhz) | |
29 | * (assume 333.3ns at 12mhz) | |
30 | * ez-usb trm 12.1 | |
31 | * Includes the cycles for each instruction | |
32 | **/ | |
33 | WORD loop_count; | |
34 | volatile WORD count; // NOTE perhaps use different solutions w/ out volatile | |
35 | ||
36 | ||
37 | // set count to the number of times we need to | |
38 | // go around a loop for 1 millisecond | |
39 | ||
40 | // then do that loop millis times. (1000 us=1ms) | |
41 | ||
42 | // 48mhz: 1000 us / (17 cycles * 83.3 ns / cycle / 1000 ns/us) = 706 | |
43 | // 24mhz: 353 | |
44 | // 12mhz: 177 | |
45 | // recalculate if the number of cycles changes | |
46 | // like if you change the loop below | |
47 | loop_count = CPUFREQ == CLK_12M ? 177 : | |
48 | CPUFREQ == CLK_24M ? 353 : 706; | |
49 | ||
50 | // sdcc generated assembly | |
51 | /* cycles code | |
52 | ; delay.c:31: do { | |
53 | 00101$: | |
54 | ; delay.c:32: } while ( --count ); | |
55 | 2 dec _delay_count_1_1 | |
56 | 2 mov a,#0xff | |
57 | 4 cjne a,_delay_count_1_1,00121$ | |
58 | 2 dec (_delay_count_1_1 + 1) | |
59 | 00121$: | |
60 | 2 mov a,_delay_count_1_1 | |
61 | 2 orl a,(_delay_count_1_1 + 1) | |
62 | 3 jnz 00101$ | |
63 | ||
64 | Total 17 | |
65 | */ | |
66 | ||
67 | do { | |
68 | count = loop_count; | |
69 | do { | |
70 | } while ( --count ); | |
71 | } while ( --millis ); | |
72 | ||
73 | } |