The 5-Minute Rule for What Is Rs485 Cable > 자유게시판

For example, at 4800 baud (bits per second), each bit lasts about 200 microseconds (µs), and if communications are full duplex (e.g., if the QVGA Controller echoes each incoming character), then there is a serial interrupt every 100 µs or so. This cable is usually 24AWG. Category-5 cable will generally work well in most instances even though its characteristic impedance is 100 Ohms. Even though some IC manufacturers offer light loading devices, that can accommodate 256 or even 400 nodes on one RS485 network, you may NOT want to build such a network for a few reasons. Even though the MOSI pin is not connected to anything, the master initiates a transmission using a "dummy" byte. An RS485 transceiver is present on the QVGA Controller, and its data direction is controlled by pin 4 of port PPC of the peripheral interface adapter (PIA). The QVGA Controller, however, does not implement hardware handshaking. The primary serial port, Serial1, is supported by the 68HC11's on-chip hardware UART, and does not require interrupts to work properly. For example, an Automatic RS232 to RS485 converter, could be connected to a computer's RS232, full-duplex port, and transform it into an RS485 half-duplex, multi-drop network at distances up to 4000ft. Converters in most instances, pass data through the interface without changing the timing and/or protocol.

In addition there is no good way to add terminations resistors at the ends of a "star" network. Thus in Table 11 5 , RTS1 is connected to CTS1, and DSR1 is connected to DTR1 onboard the QVGA Controller using zero ohm shorting resistors. Thus in Table 9 6 , RTS1 is connected to CTS1, and DSR1 is connected to DTR1 and DCD1 onboard the QScreen Controller using zero ohm shorting resistors. We can gain insight into the operation of the RS232 protocol by examining the signal connections used for the primary serial port in Table 11 5. The transmit and receive data signals carry the messages being communicated between the QVGA Controller and the PC or terminal. The QVGA Controller’s transmit data signal TxD1 (pin 2 on the 9-pin serial connector) is connected to the terminal’s receive data signal RxD (pin 2 on its 9-pin connector). Likewise, the terminal’s transmit signal TxD is connected to the QVGA Controller’s receive signal RxD1. To provide a convenient means of attaching two grounds to the serial cable, there are several pins (labeled DGND) on the communications connector that are connected to the controller’s ground plane. To provide a convenient means of attaching two grounds to the serial cable, there are several pins (labeled GND) on the communications connector that are connected to the controller’s ground plane.

In this case, cable connections must be made to Serial 1 at pins 5 and 6 of the 10-pin Serial Communications Header. Table 11-5 Serial Cable Connections. Table 11 5 shows the connection diagram for a standard 9-pin serial cable. The pinout of the Communications Connector (H14) is shown in Table 11 2, and the following diagrams show how these signals map to the two serial communications connectors. The primary and secondary serial communications ports are accessible through the QVGA Controller's 10 pin, dual row Communications Connector (H14) and through the individual Serial 1 and Serial 2 connectors. Most newer consumer electronics comes with an USB, Firewire or other high-speed communication port, however a lot of industrial and commercial equipment, both old and new, is made only with a RS485 or RS422 serial communications port. An "Automatic Converter" (RS232 to RS485) will turn on the RS485 transmitter when data is detected on the RS232 port, and revert back into the receive mode after a character has been sent. To enable the secondary serial port, turn dip switch 5 (labeled "2COM") on the QED Board ON.

A serial communications cable is supplied with QVGA Starter Kits. The QVGA Controller offers a unique addition to full duplex RS232: it can place its RS232 transmitter into a high impedance silent mode under software control. R.E.Smith also provides an extensive line of optical/transformer isolated repeaters and multi-port repeaters as well as a series of fiber optic products which provide very high isolation. The application's various editions include features for filtering, browsing, searching, recording, and data playback.Serial Monitor provides not only a wide range of visualization tools for popular serial protocols (including PPP, MODBUS, BACnet MSTP) and raw data, but also utilities for creating your own custom visualizers, allowing you to parse any data and custom protocols in a convenient way. Flexible Allows you to configure the way it displays raw data streams. First part displays each monitored packet parsed according to specified set of protocols. Some of these converters can convert from RS232 to both RS485 and RS422 however many standard models only has one of the protocols. However since only a true RS485 network can have addressable serial RS485 devices, the RS232 converter needs to be addressable either by software or by DIP switches when using it in this type of configuration.

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