keil c51程序设计精确延时方法（Keil C51 programming precise delay method）.docVIP

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keil c51程序设计精确延时方法（Keil C51 programming precise delay method）.doc

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keil c51程序设计精确延时方法（Keil C51 programming precise delay method）

keil c51程序设计精确延时方法（Keil C51 programming precise delay method） There are usually two ways to achieve the delay: one is hardware delay, the other is the use of timer / counter to achieve accurate delay; the other is software delay, mainly using the loop body. 1 use timer / counter to achieve accurate delay Monolithic integrated circuit system usually selects 11.0592MHz, 12MHz or 6MHz 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 crystal oscillator with a frequency of 12MHz. The longest delay time is up to 65536 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 the 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 2.1 transient delay In the C file by using _NOP_ () function definition statement, a series of different delay function, such as Delay10us (Delay25us), Delay40us (), () stored in a custom C file, when required in the main program called directly. If the delay 10 s delay function can be written as follows: Void,