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Bit and framing protocols are in layer two of the OSI model. Now, let’s take a look at the main differences between the two protocols. The primary difference between RS-422 and RS-485 is that RS-485 requires two wires in a single pair which all devices transmitters and receivers are connected to, and RS-422 typically uses two or more pair in which only one transmitter and up to ten receivers are connected to a single pair. This third example would be a good place to use an isolating RS-485 transceiver. The RS-485 standard is obsolete and has been superseded by TIA-485, but many if not most engineers and applications guides continue to use the RS designation even though it has officially changed. RS-485 and RS-422 can interoperate with certain restrictions. RS-485 supports inexpensive local networks and multidrop communications links, using the same differential signaling over twisted pair as RS-422. RS-422 and RS-485 Standards Overview and System Configurations, Application Report (pdf). A RS-485 interface will usually use pins 7 and 8 for the two data lines, RS485 standard since they comprise a twisted pair. Therefore we will use the term "converter" in the following. The USB to RS485 Converter is a cost-effective module for transfer serial data over USB.

2. USB Cable 1m. & Driver CDROM. A USB to serial converter typically can convert USB to either RS232, RS485 or RS422 signals. RS485 drivers : Up to 1200 m. It supports maximum data rates at a length of 1200 meters, making the RS485 protocol an excellent choice for communication between physically distant pieces of equipment. Typically the bit sequence is generated by a UART inside a microcontroller, which is wired to a RS-485 interface IC (also called a "RS485 Line Driver/Receivers" or "RS-485/RS422 Transceiver"). Another RS-232 to RS485 scheme is to monitor the data stream going into the RS-485 transmitter and trigger a one-shot timer when an edge occurs. RS-485 does not define a communication protocol; merely an electrical interface. The protocol enables communication between a single transmitter and receiver. Conversion enables older devices to coexist with new hardware that lacks serial interfaces. 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 processing terminal equipment and data communication equipment. Devices using the RS232 protocol are limited to a distance of 15 meters between transmitter and receiver while still achieving the maximum data transmission rate. The transmission speed possible with an RS232 interface is 1Mb/s for a distance of up to 15 meters. An RS232 interface is a system based on voltage levels and performs optimally in situations where there are minimal differences in ground potential. 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. There is no hardware handshaking in the RS-485 standard and in most cases it is no longer needed. Converters that changed the RS-232 electrical levels to RS-485 levels were developed which allow the serial port to transfer data over much longer distances than the RS-232 levels allowed. 200mV. This can cause a problem if the RS-485 network is using a UART to transmit data.

Another problem with this scheme is that the transmitter needs to stay enabled during the transmission of all of the data. The difference between an adapter and a converter generally is that an adapter usually only adapts the physical interface of a device to match a different type of physical interface of a different device whereas a converter converts the actual data stream between two devices. RS-232 defines thirteen "standard" interface types lettered A through M. None of these match IBM's implementation of its serial port. RS-232 is only defined for point-to-point connections, so you need a separate cable for each sensor connected to a host CPU. The two values provide a sufficient margin for a reliable data transmission even under severe signal degradation across the cable and connectors. When IBM changed to the new connector they also changed the electrical signal levels. 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. Then it references section 2.1.4 where the maximum capacitance of the receiver side of the interface point, including the cable, shall not exceed 2500pF. Then suggests seeing appendix A for guidance (again, the appendix states that it is not a formal part of the standard).