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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. 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. For Serial2 RS485 operation: Install the jumper shunt onto "2 485En" (J7). That places a 120 Ω resistor across the RS485 differential line at the driver chip. RC termination - In some applications requiring low power you may not want to load the line with 120 Ω resistors at each end. 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. In this case, cable connections may be made to Serial 2 at pins 4 and 10 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. In that case, do not install jumper caps at the jumpers labeled "Term" or "RTerm".

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". They should generally not be needed, except if you use long cables, multiple RS485 devices, and resistive termination. Because all of the serial I/O routines on the QScreen Controller are revectorable, it is very easy to change the serial port in use without modifying any high level code. 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. We assume that you are now communicating with the PDQ Board via the default Serial1 port at the standard 115200 baud rate. If it doesn’t, confirm that the terminal’s baud rate is correct by selecting the Comm item in the Settings menu of the Mosaic Terminal program, and click on 115200 baud. 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 maximum sustainable baud rate on the secondary serial port is 4800 baud. 1 running at the prior established baud rate (typically 115200 baud). So long as the error between the actual baud rate and that specified is less than 1.5% (or the error between transmitter and receiver is less than 3%) there should be no communication errors. Port to modem communications usually use 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 baud. Once the project is open, click Build→ Build, and after the compilation is done, enter the Mosaic Terminal by clicking Tools→ Mosaic Terminal and use the Send File menu item to send GETSTART.DLF to the PDQ Board. The USE.SERIAL2 command means that the operating system’s terminal interface now communicates via Serial2. High (mark) parity means that the parity bit is always logic 1 at the UART, and low (space) parity means that the parity bit is always logic 0 at the UART.

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. After configuring the SPI system to communicate on a properly connected network of devices, sending and receiving data is as simple as writing and reading a register. Only one active master may control the network at a time; however, the device that assumes the role of master may change according to an appropriate protocol. 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. 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. 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.