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一、RS-232C标准 RS-232C标准是由美国电子工程学会推荐的串行通信标准,也称EIA标准。它规定了一个25芯引线的连接器,分成两个通道组。第一通道组常用作传输数据,第二通道组常用作信息控制。在实际应用中,常常仅使用第一通道组。它规定+3V～+15V之间的任意电压表示逻辑“0”电平,-3V～-15V之间的住意电压表示逻辑“1”电平。用芯片SN75150,MC1488等实现TTL电平到EIA电平的转换,用芯片SN75154、MC1489等实现EIA电平到TTL电平的转换。连接示意图如图1所示。
First, the RS-232C standard RS-232C standard by the United States Institute of Electrical Engineering recommended serial communication standard, also known as EIA standards. It defines a 25-pin lead connector that splits into two channel groups. The first channel group is often used for data transmission and the second channel group is often used for information control. In practical applications, only the first channel group is often used. It states that any voltage between + 3V and + 15V indicates a logic “0” level, and a nominal voltage between -3V and -15V indicates a logic “1” level. With the chip SN75150, MC1488 TTL level to achieve EIA level conversion, chip SN75154, MC1489 EIA level to achieve TTL level conversion. Connection diagram shown in Figure 1.