题目详情

RS-232-C是目前常见的一种接口标准,它是由EIA组织制定的。该标准的设计数据速率是()b/s。

  • A.6400
  • B.9600
  • C.19200
  • D.20000

正确答案及解析

正确答案
D
解析

RS-232-C是由电子工业协会(EIA,ElectronicIndustriesAssociation)制定的数据终端设备和数据电路端与设备连接的物理接口标准,属于国际标准化组织ISO的开放系统互连(OSI)模型中的最低层,即物理层的协议标准。它规定了接口的机械、电气、规程和功能四个特性。RS-232-C规定的机械特性是25针的插头/座,减去一些未定义的针外,实际上只定义了20根针的功能。用来连接两个设备至少要连接3根线,即信号地、发送数据和接收数据线。在采用RS-232-C连接计算机与终端的场合就只使用这3根线。RS-232-C的设计数据速率是20000b/s,连接设备间的距离也有规定。为了实现更高的数据速率和更远的距离连接,EIA又制定了另一个RS-422标准。该标准的电气特性与RS-232-C不同,不用公共地,采用双线平衡传输的方式,在同样的数据速率条件下,可达到较远的传输距离。在数据速率为20000b/s时,连接设备间的距离可扩展到原有RS-232-C标准的约80倍。

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