RS-232 Technology Basics

Overview:
-History:
Place RS-232 History Here

-Theory of Operation:
Signal Levels:
We know that the specifications of RS-232 technology used on a PC's COM port range from -15V to +15V and will distinguish -5V to +5V signals as a low, and -10V>> signals >>+10V as a high.

Typical RS-232 Setup, Connectors, Signals:

Transmission Concept:
We will want to set up an interface so that it resembels a PC to PC (DTE to DTE) transmission circuit, or commonly called a "Null Modem or Crossover Cable". The Picture below shows the concept of transmission between two PCs (DTEs) using RS-232 technology.

In our case, since one of the "PC's" or DTEs is a CMOS standard device simply crossing connections as seen above will not work. In fact if you attempt to replace one of the PCs seen above with a Dreamcast, you will likely have fried the serial UART of the Dreamcast. However, if we place a signal "converters" (transceiver IC) intercepting the lines of transmission, the voltage levels can be correctly converted.

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