7 Sensible Ways to show Rs485 Cable Into a Sales Machine > 자유게시판

In these distributed processing networks, a variety of machines and instruments work locally, but communicate and share data or resources with one another globally using a single serial link. The advantage of using Serial1 for RS485 is that the Serial1 RS485 signals are also available on the Docking Panel, while the Serial2 RS485 signals are available only on the PDQ Board’s Serial Communications Header. From the PDQ Board’s point of view, these three signals (/TxD, /RxD, and ground) are the only connections required to perform serial communications. The secondary serial port is connected similarly except that the onboard connection of /RTS to /CTS, and /DSR to /DTR are permanent. A jumper labeled "2 485En" (J7) enables RS485 operation on the Serial2 port if the jumper cap is installed, and configures Serial2 for RS232 operation if the jumper cap is not installed. What made it such an advancement over RS232 was the fact that it could transmit not only a single device to device transmission, but also a communications bus to connect multiple devices at once. 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 QScreen Controller echoes each incoming character), then there is a serial interrupt every 100 µs or so.

RS485Receive() to wait for any pending character transmission to complete, then disable the transmitter, and then execute a routine such as Key() to listen to the communications on the serial bus. If PT is cleared, then all transmitted bytes with a parity bit will have an even number of total '1' bits. The PT bit, with mask 0x01, determines whether even parity or odd parity is used if parity bit generation is enabled. The PE bit, with mask 0x02, determines whether the most-significant bit in each byte is used as a parity bit. The above parity settings will also determine how incoming data is interpreted (whether the most significant bit is considered a parity bit or part of the data being transmitted, and how many bits total to expect in each byte). So, for eight data bits with a parity bit, M would be set (equal to one) in order to add an extra bit to each byte transmitted, and PE would be set in order to make that extra bit be used as a parity bit. The RS232 protocol provides for four handshaking signals called ready to send (RTS), clear to send (CTS), data set ready (DSR), and data terminal ready (DTR) to coordinate the transfer of information.

A jumper labeled "1 485En" (J4) enables RS485 operation on the Serial1 port if the jumper cap is installed, and configures Serial1 for RS232 operation if the jumper cap is not installed. For Serial1 RS485 operation: Install the jumper shunt onto "1 485En" (J4). For Serial2 RS232 operation: Remove the jumper shunt from "2 485En" (J7). For Serial2 RS485 operation: Install the jumper shunt onto "2 485En" (J7). Alarm systems: Rs485 cables in alarm systems help transfer alarm signals and information from alarm devices to the control center. With your RS485 network, you can remotely monitor and control that pump from a control center. The PLC is also connected to the VFD via RS485. RS485Init() configures PORTJ to ensure that bits 0 and 1 are outputs, and disables both RS485 transmitters, leaving the Serial1 and Serial2 RS485 channels in receive mode. Because all of the serial I/O routines on the PDQ Board are revectorable, it is very easy to change the serial port in use without modifying any high level code. We’ll use code from the GETSTART.C program. 1. Use 0603 SMT sized resistor packages.

In that case you may terminate the lines with a series RC network comprising a 0.1 μF capacitor in series with a 120 Ω resistor. While running this program, the parity settings of Mosaic Terminal may be adjusted, and in each case the message that matches current settings will appear clearly while the other messages will appear garbled. Many terminals and PCs, however, do rely on hardware handshaking to determine when the other party (in this case the PDQ Board) is ready to accept data. Most modems communicate using RS232 and a set of hardware handshaking signals used to regulate data flow. Because we chose the default baud rate (which the terminal is presumably already set for), you can simply move the serial cable from the Serial Port 1 connector to the Serial Port 2 connector on the Docking Panel to complete the change to the new port. No termination - If the PDQ Board is not an end device, you should not terminate that cable. Resistive termination - If the PDQ Board is at the end of the RS485 cable you can terminate the cable by installing jumper caps at both jumper locations, "Term" and "RTerm".