?????????Щ??????????????
??????????????????????????????????????????/??????????????????????CPU?????Ч????????????????;?????????????????????????????????????С?????????51????????????
1 ???????/??????????????
?????????????11.059 2 MHz??12 MHz??6 MHz???????????????????????????????????????????????????1 μs??2 μs????????????????????м??????????12 MHz?????????????????216=65 536 μs?????????????????2????????????????????;??????????????????????????????????????(??????????????2??????????)??
?????????У???????????ж??????????????????????????????????????????????????/??????????????????Ч?????????????濼??????????????????????C51??д???ж???????????????????PUSH ACC??PUSH PSW??POP PSW??POP ACC????????????4??????????;??????л??м??????1???????????1?????????????Щ?????????????????????????????????????м???????С????????
2 ???????????????
???????????????/?????????????????????????????????????????????????????????????????????????
2.1 ???????
??????C????????????_NOP_( )??????????????????в???????????????Delay10us( )??Delay25us( )??Delay40us( )???????????????C????У????????????????????á??????10 μs????????????д?????
void Delay10us( ) {
_NOP_( );
_NOP_( );
_NOP_( );
_NOP_( );
_NOP_( );
_NOP_( );
}
Delay10us( )?????й?????6??_NOP_( )????????????????1 μs????????????Delay10us( )???????????LCALL???(2 μs)????????6??_NOP_( )???(6 μs)?????????????RET???(2 μs)???????????????????????10 μs??????????????????????????????????????????????е????????????[4]????????????????;????????????Delay40us( )????????4??Delay10us( )????????????????佫??42 μs????????40 μs????????????Delay40us( )?????????????LCALL???(2 μs)????????е????Delay10us( )?????????????Delay10us( )?????????????????????????????????????????????Delay80us( )?????ε???Delay40us( )??????????????LCALL???(2 μs)????????????Delay40us( )????(84 μs)?????????????????86 μs????????????????????????RET??䶮?????????????????????????????????Delay80μs( )????????8??Delay10us( )??????????????82 μs??????????????????????????????????????????????????????????
2.2 ??C51?????????????????
??C51?????????????#pragma asm??#pragma endasm?????????????????????д?????????????#pragma asm?????#pragma endasm????????
?磺#pragma asm
…
???????????
…
#pragma endasm
?????????????????????????????????unsigned char??int??long????????????????????????????????????????λ??R7??R7R6??R7R6R5?С??????????????????
?? #pragma asm??#pragma endasm????????????;
?? ?????????????????????#pragma asm???????????????????????????????;
?? ?????asm????????????????????????飬?????????????;
?? asm?????Сд??????????asmд???д???????????????????????;
?? #pragma asm??#pragma endasm?? asm????????????á?
???????????C51?????????????????????????????????????????????????
2.3 ?????????????????
?????????????????????????????????????д??????????????????ú????????????I/O??????P1.0???????????????????P1.0??????????????????????????????????????????????P1.0????????????伴?????????????????????????????
sbit T_point = P1^0;
void Dly1ms(void) {
unsigned int i,j;
while (1) {
T_point = 1;
for(i=0;i<2;i++){
for(j=0;j<124;j++){;}
}
T_point = 0;
for(i=0;i<1;i++){
for(j=0;j<124;j++){;}
}
}
}
void main (void) {
Dly1ms();
}
??P1.0?????????????????????????????P1.0???????????????3 ms??????????У??????2 ms???????1 ms????for?????“for(j=0;j<124;j++) {;}”?????????1 ms??????????????????????????????????????????????for?????????????????????????????????????????????
2.4 ??÷???????????????
??Keil C51?е?????????????????????????п??????????????????????????????????ó???????????????????????“for (i=0;i
C:0x000FE4CLRA//1T
C:0x0010FEMOVR6,A//1T
C:0x0011EEMOVA,R6//1T
C:0x0012C3CLRC//1T
C:0x00139FSUBBA,DlyT //1T
C:0x00145003JNCC:0019//2T
C:0x00160E INCR6//1T
C:0x001780F8SJMPC:0011//2T
?????????0x000F??0x0017???8????????????????????????????????DlyT?Ρ???????????0x0011~0x0017??6????????8?????????????1??????????“CLR A”??“MOV R6??A”??????????2???????????????1?????8????????????????1????????5???????????DlyT?κ?????????????(2+DlyT×8+5)???????????????????12 MHz????????7 μs??
??????while (DlyT--)????????DlyT????????R7?С?????????????????
C:0x000FAE07MOVR6, R7//1T
C:0x00111F DECR7//1T
C:0x0012EE MOVA,R6//1T
C:0x001370FAJNZC:000F//2T
????????е?????(DlyT+1)×5????????????????????????????????5 μs??
?????鷢????罫while (DlyT--)???while (--DlyT)?????????????????????
C:0x0014DFFE DJNZR7,C:0014//2T
???????????????????1???????2????????????????2 μs?????????DlyT×2??????????;???????????DlyT?????????0??
????????????????????????ú?????????2?????????????
???????????
????admin ?????????2018-05-19
