51 Details of Single Chip Microcomputer 1S Time Design Description

#include SBIT P1_0 = P1 ^ 0; Void delay (); // Be sure to consistent with the case here, there will be warnings or errors void main () { While (1) // Started a loop { P1_0 = 0; DELAY (); // There is no parameter to add () otherwise Warning P1_0 = 1; DELAY (); } } Void delay () / / 12M crystal 1S delay { UNSIGNED CHAR H, I, J, K; For (h = 5; h "0; H -) For (i = 4; i "0; I -) For (j = 116; j "0; J -) For (k = 214; k "0; k -); // The last must be; } / / ===================== // Principle, using the H, I, J, and K cycle instructions to consume a certain time to reach the delay, why use the loop delay method, and the four variables of H, I, J, K, and in 1 second in 12M crystal. The value of each variable is in the above code? This is to start from the cycle of the microcontroller, the single chip has an instruction cycle, the machine cycle, the state period, the clock cycle; Clock cycle: Also on the oscillation cycle of the crystal oscillator as an example, the clock cycle is 1/12000000 = 1/12 elw; Machine cycle: 1 machine cycle = 6 status cycles = 12 clock cycles = 1us Instruction Period: The time required for the single chip performs a command is called an instruction cycle, and the instruction cycle is not necessarily the same as the machine cycle, and the machine cycle required for different instructions is not necessarily the same (1-4), and the single-chip performs a single-cycle instruction. It takes 1us to execute a two-cycle instruction requires 2us, and the for loop requires 8 instruction cycles; Specifically perform the time of the FOR cycle consumption, you can pass the code measurement in KEIL: #include SBIT P1_0 = P1 ^ 0; Void delay (); void main () { While (1) // Started a loop { P1_0 = 0; DELAY (); P1_0 = 1; DELAY (); } } Void delay () { UNSIGNED Char H; For (h = 1000; h "0; h -); // This is broken } Circular 1000 times of execution of time points 0.00042850S - 0.00019600S = 0.00023250S = 232.5Us; 1 cycle consumption is about 0.2us, 1S = 1000000US, 1000000US / 0.2US = 500000 times, while 5 * 4 * 116 * 214 = 496480; because unsigned characters Unsigned Char size is 1 byte, the range is 0 ~ 255, so it can only be completed, approximation Get a 1S delay. , Read full text, original title: 51 single-chip 1S delay program design Article Source: [Micro Signal: Changxuemcu, WeChat Public Number: Study Mechanical Machine] Welcome to add attention! Please indicate the source of the article.

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