DTR/DSR 和 RTS/CTS 流控有什么区别? [英] What is the difference between DTR/DSR and RTS/CTS flow control?

问题描述

DTR/DSR 和 RTS/CTS 硬件流控有什么区别?每个什么时候用?为什么我们需要不止一种硬件流控?:)

What's the difference between DTR/DSR and RTS/CTS hardware flow control? When is each one used? Why do we need more than one kind of hardware flow control? :)

推荐答案

• DTR - 数据终端就绪
• DSR - 数据集就绪
• RTS - 请求发送
• CTS - 允许发送

有多种做事方式，因为标准中从来没有内置任何协议.您可以使用您的设备实现的任何特别标准".

There are multiple ways of doing things because there were never any protocols built into the standards. You use whatever ad-hoc "standard" your equipment implements.

仅根据名称，RTS/CTS 似乎是天作之合.然而，它与随着时间发展的需求背道而驰.这些信号是在终端批量发送充满数据的屏幕时创建的，但接收器可能尚未准备好，因此需要流量控制.稍后问题将得到逆转，因为终端无法跟上来自主机的数据，但是 RTS/CTS 信号走错了方向 - 接口不是正交的，并且没有相应的信号走另一条路.设备制造商尽其所能进行调整，包括使用 DTR 和 DSR 信号.

Just based on the names, RTS/CTS would seem to be a natural fit. However, it's backwards from the needs that developed over time. These signals were created at a time when a terminal would batch-send a screen full of data, but the receiver might not be ready, thus the need for flow control. Later the problem would be reversed, as the terminal couldn't keep up with data coming from the host, but the RTS/CTS signals go the wrong direction - the interface isn't orthogonal, and there's no corresponding signals going the other way. Equipment makers adapted as best they could, including using the DTR and DSR signals.

编辑

要添加更多细节，它是一个两级层次结构，因此正式"两者都必须发生才能进行通信.该行为在原始 CCITT(现为 ITU-T)标准 V.28 中定义.

To add a bit more detail, its a two level hierarchy so "officially" both must happen for communication to take place. The behavior is defined in the original CCITT (now ITU-T) standard V.28.

DCE 是连接终端和电话网络的调制解调器.在电话网络中是另一件分离到数据网络的设备，例如.X.25.

The DCE is a modem connecting between the terminal and telephone network. In the telephone network was another piece of equipment which split off to the data network, eg. X.25.

调制解调器具有三种状态:电源关闭、就绪(Data Set Ready 为真)和已连接(Data Carrier Detect)

The modem has three states: Powered off, Ready (Data Set Ready is true), and connected (Data Carrier Detect)

在连接调制解调器之前终端不能做任何事情.

The terminal can't do anything until the modem is connected.

当调制解调器想要发送数据时，它会引发 RTS 并且调制解调器使用 CTS 批准请求.调制解调器在其内部缓冲区已满时降低 CTS.

When the modem wants to send data, it raises RTS and the modem grants the request with CTS. The modem lowers CTS when its internal buffer is full.

好怀旧！

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