Again many thought that the UART protocol used in the serial port were part of the RS-485 standard, but the RS-485 standard contains even less of the OSI model layer one than RS-232 does. Many think the RS-232 standard completely defines the IBM PC serial port, but this is incorrect. When configuring an IBM PC’s serial port, the parity, number of data bits, and number of stop bits must be set; therefore, many think this must be part of the RS-232 standard. A circuit is a full definition of a signal from the transmitting device to the receiving device, but many now think of these definitions as pin labels. Another figure in the annex (again, the annexes are not considered to be part of the standards) discusses connecting the "Green Wire Ground of Power System" or "Protective Ground or Frame Ground" to "Circuit Common or Circuit Ground" and "SC Signal Common". Layer two of the OSI model includes the bit and framing protocol, which is outside of these EIA/TIA standards. Neither standard includes any of the OSI model layer two, where the bit framing protocol resides.

The foreword to the standard references The Telecommunications Systems Bulletin TSB-89 which contains application guidelines, including data signaling rate vs. Many references and examples are made to "asynchronous start-stop communication with a UART" or "UART" communications. A serial interface is a very good option for communications over any distance greater than several feet. The "pin mislabeling" discussed above is a good starting point. This standard is for up to 21 circuits on a 25 pin DB-25 connector. Another example of misunderstanding the RS-232 standard is the 9-pin connector. The serial port used a D-sub, B-shell, 25-pin connector (commonly called a DB-25) and RS-232 electrical signal levels, which made it "RS-232 compatible" or compatible with the RS-232 standard. This serial port was no longer a "RS-232 compatible" serial port since the connector and signal levels no longer matched the RS-232 standard. In summary, the EIA/TIA standards (which are commonly miscalled RS standards) are the physical layer which include electrical signal levels and RS-232 includes the connector. The IHS Standards Store has relabeled all of the 232 standards as TIA-232. In reality, the only viable option for long lines is twisted pair, but the standards do not require it. It does not mean that this protocol is part of the standards or that only this protocol may be used with the 232/422/485 standards.

All three standards have annexes. It's a nice to have feature if you have space for it. What is Variable Frequency Drive? The LTC2862-LTC2865 excel in rejecting large amplitude, high frequency and high slew rate common mode perturbations. One circuit (Signal Common) is required for all interface types. The RS-232 standard title is "Interface Between Data Terminal Equipment and Data Circuit Terminating Equipment Employing Serial Binary Data Interchange". It defines a means of exchanging control signals and binary serialized data signals between data terminal equipment and a data communication channel in cases where interchange point. The RS-232 standard defines a DB-25 and a 26-pin alternate connector, the function of each of the pins in the connector (called circuits), and the electrical characteristics of the signals that are on the "circuits". EIA/TIA-574 is the standard for 9-pin connectors, and EIA/TIA-561 is a standard for 8-pin connectors that are commonly used with serial ports. RS-232 specifies two connectors, a 25-pin (DB-25) and an alternate 26-pin connector (pin 26 is "No Connection"). The connector resides in layer one of the OSI model and RS-232 includes the connector. A serial port could be added with a card that plugged into one of the ISA expansion slots.

When an RS-485 driver gets its data directly from a UART (with no added inversion), you would expect the "A" and "B" wires to match the voltages in the RS-485 standard for the voltages on the wires, but they will not (unless the driver inverts its input). PURPOSE AND SCOPE OF COVERAGE - This standard is applicable to the interconnection of data terminal equipment (DTE) and data circuit-terminal equipment (DCE) employing serial binary data interchange. PURPOSE AND SCOPE OF COVERAGE - This standard is applicable to the interconnection of data terminal equipment (DTE) and data communication equipment (DCE) employing serial binary data interchange. PURPOSE AND SCOPE OF COVERAGE - This standard is applicable to the interconnection of data terminal equipment (DTE) and data circuit-terminating equipment (DCE) employing serial binary data interchange. Figure 1 of the RS-485 standard is a diagram (not shown for copyright concerns) which shows the "balanced interconnecting cable" as a transmission line of two wires. The RS-232 standard does not include a line length limit, but practical limits of the electrical signal levels prevent long lengths. The RS-485 standard calls for a differential signaling scheme that will operate over a much longer line length than RS-232 can.

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