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MCS-48单片机有27根I/O线,能满足一般场合的应用,但是当应用系统需配备各种外设(如键盘、显示器等)时,或进行工业控制(工业控制需相当数量的I/O点数)时,芯片的I/O线就不够用了,此时就需要进行扩展。MCS-48单片机允许四种I/O扩展方式:一、使用一个特别的廉价扩展器8243;二、用标准的MCS-0185 I/O器件扩展;三、可用存贮器、I/O组合扩展器件进行扩展(如8155、8355等);四、也可用标准TTL(74系列)器件扩展。一、通过扩展器8243进行扩展对于小系统,最有效的I/O扩展方法是使用8243扩展器。8243是专门为MCS-48单片机设计的一种廉价的4位I/O扩展芯片,可以扩展4个4位I/0口,MCS-48单片机
MCS-48 microcontroller has 27 I / O lines to meet the needs of general applications, but when the application system needs to be equipped with a variety of peripherals (such as keyboards, monitors, etc.), or industrial control (industrial control requires a considerable amount of I / O points), the chip’s I / O line is not enough, at this time need to be extended. MCS-48 single-chip allows four I / O expansion: First, the use of a special low-cost expander 8243; Second, with the standard MCS-0185 I / O device expansion; Third, the available memory, I / O portfolio expansion Device expansion (such as 8155,8355, etc.); Fourth, also available standard TTL (74 series) device expansion. First, the expansion through the expander 8243 For small systems, the most effective way to expand I / O is to use the 8243 expander. 8243 is a low-cost 4-bit I / O expansion chip specially designed for MCS-48 microcontroller, which can expand 4 4-bit I / 0 ports and MCS-48 singlechip