单片机c语言（Singlechip c language）.docVIP

单片机c语言（Singlechip c language） Here are some questions you should pay attention to when designing the delay subroutine in C51 1, in C51 for precise delay subroutine design, try not to Or less local variables are defined in the delay subroutine, and all the delays are sub - processes Variables in a sequence are passed by a reference function. 2 、 in the design of time delay subroutine, adopt do... While, the structure goes around The ring body is better than the for structure in the loop body. 3, in the design of the delay subroutine, the loop body should be nested In the first cycle, then decrease than the first minus, then internal circulation is better. Unsigned, char, delay (unsigned, char, I, unsigned, char, J, unsigned, char, K) {unsigned, char, B, c; B= j; C= k; Do{ Do{ Do{k--}; While (K); K= c; J--;}; While (J); J=b; I--;}; While (I); } This precise delay subroutine is compiled by C51 to complete the following instruction set Delay delay subroutine is as follows: MOV, R6, 05H MOV, R4, 03H C0012:DJNZ, R3, C0012 MOV, R3, 04H DJNZ, R5, C0012 MOV, R5, 06H DJNZ, R7, C0012 RET Assume that the initial value of the parameter variable I is m, and the initial value of the parameter variable J is n The initial value of the variable K is l, the total delay time is: L * (n * (m * T2T) 2T 3T), Where T is the execution time of the DJNZ and MOV instructions. When m=n=l, the exact delay is 9T, the shortest; When m=n=l=256, the exact delay to is the longest. ----------------------------------------------------------------------------------------- The method of software timing calculation is adopted Using the instruction execution cycle setting, the following is a time delay program: Instruction cycle MOV 1 DJNZ 2 NOP 1 The use of cycle mode timing, there are procedures: MOV, R5, #TIME2; cycle 1 LOOP1:, MOV, R6, #TIME1; 1 LOOP2: NOP; 1 NOP; 1 DJNZ, R6, LOOP2; 2 DJNZ, R5, LOOP1; 2 Timing number = (TIME1*4+2+1) *TIM2*2+4 Just learned another one, using _nop_ (), remember