The Ins and Outs of the TTL Interface
串行通信可在相当长的距离内传输数据，通常与 TTL 标准有关。数据通过串行通信传输，串行通信通过单线传输比特位。数据通过双方--发送方和接收方--以二进制脉冲的形式使用各种串行数字二进制技术进行交换。
RS232 是最早的串行通信协议形式之一，至今仍被串行端口广泛用于连接计算机和设备。它逐位发送数据，非常类似于微控制器的串行信号。这一标准源自 TTL。晶体管-晶体管逻辑（或 TTL）是一种串行通信类型，现代微控制器经常使用这种类型的串行通信，它采用所谓的 UART（或称为通用异步接收器/发送器传输技术）。
| Serial communication allows for data transmission over considerable distances and is commonly associated with the TTL standard. Data is transferred through serial communication, which transmits bits at a time over a single wire. Data is exchanged using two parties—the transmitter and receiver—by using various serial digital binary technologies in the form of binary pulses. One of the first forms of serial communication protocol, RS232, is still widely used today by serial ports to connect computers to devices. It sends data bit by bit, much like serial signals from a microcontroller. This standard derived TTL. Transistor-Transistor Logic, or TTL, is a type of serial communication that is frequently used in modern microcontrollers using what is called the UART, or universally asynchronous receiver/transmitter transmission technique. |
RS232 由于年代久远，应用广泛，价格便宜，以数据传输可靠而著称。简单的布线和标准化的方法使相关硬件具有广泛的兼容性，并易于采购。同样，TTL 由于设计简单、可用性高，成本更低。由于 TTL 与微控制器高度兼容，而且非常容易使用，因此它在大多数项目中无处不在并成为行业首选也就不足为奇了。
每个 TTL 芯片通常有数百个晶体管。通常情况下，一个封装就包含了从逻辑门到 CPU 的所有功能。逻辑系列由 BJT（双极结晶体管）组成。顾名思义，晶体管有两种用途：逻辑和放大。TTL 逻辑由多个晶体管组成，每个晶体管都有多个发射极和输入端。TTL 的设计形式多种多样，可用于各种用途，例如用于太空应用的抗辐射 TTL 封装，以及在速度和低功耗之间取得良好平衡的低功耗肖特基二极管。
| RS232, due to its age and widespread adoption, is cheaply available and is known for its reliability in data transmission. The simple wiring and standardized methodology make associated hardware widely compatible and easily sourced. TTL similarly has an even lower cost due to its simple design and high availability. It is no surprise then that it is omnipresent and an industry preference for most projects as it is highly compatible with microcontrollers and is really easy to use. Each TTL chip typically has hundreds of transistors. Typically, a single package will contain everything from logic gates to a CPU. The logic family is composed of BJTs (bipolar junction transistors). As its name suggests, the transistor serves two purposes: logic and amplification. TTL logic consists of a number of transistors, each of which has a number of emitters and inputs. TTL comes in a variety of forms that are designed for various uses, such as radiation hardened TTL packages for space applications and Low power Schottky diodes that offer a great balance between speed and low power consumption. |
就功耗而言，TTL 器件的功耗通常高于 CMOS 器件，尽管 CMOS 器件的功耗并不随时钟速度的增加而增加。晶体管-晶体管逻辑比当代的 ECL 电路慢得多，但功耗却低得多，设计原理也更简单。TTL 的主要优点是与其他电路的连接简单，而且由于特定的电压电平和良好的噪声裕量，可以提供复杂的逻辑功能。扇入（Fan-in），即输入端可接受的 i/p 信号数量，也是 TTL 的强项之一。TTL 的低电平为 0 至 0.2 伏，高电平为 5 伏，扇出 10 个门，即最多可支持 10 个门。
TTL 接口是一种多功能、低成本和广泛兼容的接口，以其可靠性和可用性而著称。TTL 芯片包含许多晶体管，用于逻辑和放大，是一种简单而巧妙的设计。
| When it comes to power consumption, TTL devices typically consume more power than CMOS devices, although CMOS device power utilization does not increase with clock speed. Transistor-transistor logic is substantially slower than contemporary ECL circuits, but it uses significantly less power and has simpler design principles. The key advantage of TTL is that it is simple to link with other circuits and that it can provide complex logic functions due to particular voltage levels and good noise margins. Fan-in, or the number of i/p signals that may be accepted through an input, is also one of TTL’s strong points. TTL operates at a low level of between 0 and 0.2 volts and at a high level of 5V, and it has a fan out of 10 gates, which means that it can support up to 10 gates. The TTL interface is a versatile, low-cost, and widely compatible one that is best regarded for its reliability and availability. A TTL chip contains many transistors which serve the purposes of logic and amplification, a simple yet ingenious design. |
参考：
1，Focus LCDS
The Ins and Outs of the TTL Interface - Focus LCDs
