Three Precious Classes About Rs485 Cable That you'll Never forget

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. That places a 120 Ω resistor across the RS485 differential line at the driver chip. RS485 is another protocol supported by the primary serial port on the PDQ Board. The PDQ Board does not differentiate between these. 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". RS232 is by far the most common serial protocol, and is the default protocol for both of the PDQ Board’s serial ports. Although the maximum standard baud rate of the primary serial port is 19200 baud, nonstandard baud rates of over 80 Kbaud can be attained by the 68HC11's on-chip UART and the onboard RS232 driver. The actual baud rate produced differs from that requested by a small error owing to rounding of an internal divisor.

Baud to specify the baud rate. The BAUD routine described at the start of this subsection configures the baud rate of each of the Serial1 and Serial2 channels. Enabling RS485 on the Serial2 port is parallel to the process described above. Now select the "Comm" item in the "Settings" menu of the Terminal program, and click on 1200 baud (or whatever baud rate you selected in the command above). The default baud rate after a factory cleanup is 115200 baud. The default serial routines used to download programs to the operating system assume that full duplex communications are available, so you cannot use the RS485 protocol to program the controller. After a factory cleanup, Serial1 is the default serial port for program development and downloading. The RS485 data direction of Serial1 and Serial2 are controlled by the PJ0 and PJ1 processor pins, respectively. For Serial2 RS485 operation: Install the jumper shunt onto "2 485En" (J7). For Serial1 RS485 operation: Install the jumper shunt onto "1 485En" (J4). If your application requires RS485, you can use the secondary serial port (serial2) to program and debug your application code using the RS232 protocol, and use the primary serial port (Serial1) for RS485 communications.

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 Serial2 RS232 operation: Remove the jumper shunt from "2 485En" (J7). 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. They translate the bit-by-bit data on the serial cable into bytes of data that can be interpreted by the operating system or by your application program. The adapter includes a 3 foot 'type A' cable connection that plugs into any PC or MAC USB port. The following table shows the connection diagram for a standard 9-pin serial cable. The secondary serial port is connected similarly except that the onboard connection of /RTS to /CTS, and /DSR to /DTR are permanent. The primary and secondary serial communications ports are accessible through the PDQ Board's 10 pin, dual row Communications Header (H2) and through the Docking Panel's 10 pin, right-angle, dual row Communications Header (H1) and individual DB-9 Serial 1 and Serial 2 connectors.

The pinout of the PDQ Board’s Communications Header (H2), Docking Panel’s Communications Header (H1), and the Docking Panel’s Communications DB-9 Connectors are shown in the following tables. In this case, cable connections may be made to Serial 1 on either the 10-pin PDQ Board Serial Communications Header, or the Docking Panel’s 10-pin right-angle Serial Header, or the Docking Panel’s Serial1 DB-9 Connector. In this case, cable connections may be made to Serial 1 at pins 5 and 6 of the PDQ Board’s 10-pin Serial Header , or pins 5 and 6 of the Docking Panel’s 10-pin right-angle Serial Header. All of the RS232 signals start with the / (slash, pronounced not) character to indicate that the signals on the serial cable are logically inverted. Most computers conform to IBM PC AT-compatible RS232 interfaces which use 9-pin D-Type connectors, consequently the QScreen Controller brings out its serial ports to two female 9-pin D-Type connectors.