keil c51 精确延时程序执行时间（Keil C51 precise delay program execution time）.docVIP

keil c51 精确延时程序执行时间（Keil C51 precise delay program execution time） Keil C51 precise delay program execution time The delay usually has two methods: one is the hardware delay, to use the timer / counter, this method can improve the efficiency of the CPU, also can do accurate delay; the other is a software delay, this method is mainly used for the body. 1 use timer / counter to achieve accurate delay Monolithic integrated circuit system usually selects 11.0592 MHz, 12 MHz or 6 MHz crystal oscillator. The first one is easier to generate various standard baud rates, and the latter two are 1 s and 2 s respectively, which is convenient for precise delay. This procedure assumes the use of a crystal oscillator with a frequency of 12 MHz. The longest delay time is up to 216=65 536 Mu s. If the timer works in the way 2, you can achieve a very short time accurate delay; if the use of other timing methods, you should consider reloading the timing of the initial value (reinstall the timer, the initial value of 2 machine cycles). In practice, interrupts are often used for timing, such as performing an appropriate cycle to achieve delays of a few seconds or even longer. The use of timer / counter delay, from the programs execution efficiency and stability of two considerations, is the best solution. It should be noted that, C51 prepared by the interrupt service program compiled automatically with PUSH ACC, PUSH PSW, POP PSW and POP ACC statement execution occupies 4 machine cycles; if a program has values of 1 statements, and will take up to 1 machine cycles. The time consumed by these statements should be taken into account when calculating the initial value of the timing, and subtracted from the initial value to achieve the minimum error. 2 software delay and time calculation In many cases, timers / counters are often used for other purposes and can only be delayed by software methods at this time. Here are some software delay methods. 2.1 transient delay In the C file by using