Purpose and meaning of those physical lines, such as TX, RX, DCD, CTS etc.Electrical characteristics of the signals carried by those interconnections (voltage levels, slew rates, impedance etc).Some RS-232 variants also specify which types of connectors and cable you must use. Physical wiring, the interconnections between RS-232 compliant devices.It defines the signalling requirements for serial communication, by laying out rules and guidelines regarding: So while a UART may help you implement an RS-232 interface, it is not an RS-232 interface itself. If it does not you will have to control them with your software/firmware directly. These will also need to be level converted, and your UART may, or may not, support these signals. Further, the RS-232 standard includes the definition of several other signalling pins besides TX and RX, which you may need to use depending on the equipment you need to connect to. A complete RS-232 interface will typically involve both a UART and an RS-232 level converter. You will need to convert the output of the UART to the +/-12V standard that RS-232 requires. UARTs do not typically interface directly with RS-232. The UART can be configured to support these various protocols on its TX and RX lines. You can find older equipment that includes parity bits, or uses 7 or 9 bits. Most equipment today manufactured uses this encoding, but there's no requirement to do so. Generally, when people use RS-232, they use a simple 8 bit NRZ encoding with one start bit and one stop bit. However, neither the UART, nor the RS-232 standard define what is sent on the TX and RX lines. You know, then, that a standard RS-232 cable will connect the two. To avoid the need for special converters or cables, the manufacturers may choose to follow the RS-232 standard. While two pieces of hardware may have UARTs, you don't know that they'll connect without damage, or communicate properly unless you know they have the same pinout and voltage standards, or include a converter or specially wired cable specific to the interconnection of these two specificl devices. This is a specific interface standard that allows for equipment interoperability. RS-232 - A standard defining the signals between two devices, defining the signal names, their purpose, voltage levels, connectors and pinouts. At minimum it means that it has a TX and an RX line, which sends a serial data stream and receives a serial data stream. The term is generic, and does not represent a specific standard. The "universal" part means that it can be configured to support many different specific serial protocols. This is, essentially, a serial communications interface. UART (or USART) - Universal (Synchronous) Asynchronous Receiver/Transmitter
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