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RS232 is an Interface and the protocol between DTE(data terminal equipment) and DCE(data communication equipment) using serial binary data exchange. Here C is used for the current version. Universal Asynchronous Data Receiver & Transmitter (UART), attached in a motherboard, used in connection with RS232 for transmitting data to any serial device like modem or printer from its DTE interface.
Figure: RS 232 interface
RS-232C is a long-established standard (“C” is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication between computers and related devices. It was defined by an industry trade group, the Electronic Industries Association (EIA), originally for teletypewriter devices.
RS-232C is the interface that your computer uses to talk to and exchange data with your modem and other serial devices. Somewhere in your PC, typically on a Universal Asynchronous Receiver/Transmitter (UART) chip on your motherboard, the data from your computer is transmitted to an internal or external modem (or other serial device) from its Data Terminal Equipment (DTE) interface. Since data in your computer flows along parallel circuits and serial devices can handle only one bit at a time, the UART chip converts the groups of bits in parallel to a serial stream of bits. As your PC’s DTE agent, it also communicates with the modem or other serial device, which, in accordance with the RS-232C standard, has a complementary interface called the Data Communications Equipment (DCE) interface.
For data transfers where even more coordination is required between the sending system and the receiving system a double handshake is used the sending device asserts its stb line low to ask “ are you ready”? the receiving system raises its ack line high to say I m ready. The peripheral device then sends the byte of data and raises its stb line high to say I have the data thank you. And I wait your next request to send the next byte of data. For handshake output of this type from a microprocessor to a peripheral the waveforms are the same but the microprocessor sends the stb signal and the data the peripheral sends the ack signal. In the accompanying laboratory manual it is shown hoe to interface with a speech-synthesizer device using this type of handshake system.
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