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If your application requires RS485, use the primary serial port (serial1) for RS485 communications, and use the secondary serial port (Serial 2) to program and debug your application code using the RS232 protocol. 5 Volt supply by a dual RS232 driver chip that has a built-in charge pump voltage multiplier. RS232 uses inverse logic; that is, a positive bit at the 68HC11 UART is inverted by the onboard RS232 driver chip and appears as a negative signal on the serial cable. The primary channel’s UART translates the bit-by-bit data on the serial cable into bytes of data that can be interpreted by the QED-Forth Kernel or by your application program. The RS-485 application in heating, ventilation, rs485 cable air-conditioning unit. The secondary channel is very useful for debugging application programs that communicate with other computers or I/O via the primary channel. Serial 2 is implemented by a software UART in the controller’s QED-Forth Kernel that uses two of the processor’s PortA I/O pins to generate a serial communications channel. The Serial 1 port is implemented with the 68HC11's on-chip hardware UART (Universal Asynchronous Receiver/Transmitter). Rather, the UART deduces the correct time to sample the incoming signal based on the start and stop bits in the signal itself.

Half-duplex mode allows for communication in only one direction at a time whereas full-duplex mode allows for simultaneous bi-directional communication between devices. It is a half duplex protocol, meaning that only one party at a time may transmit data. Unlike the standard RS232 protocol, RS485 allows many communicating parties to share the same 3-wire communications cable. Powerful APP Support: SenseCAP Mate APP allows you to set the sensor templates and quickly turn the data logger into the sensor you want. If we want to connect a PC with an Unitronics PLC, for example for programming or debugging reasons, we need a connection cable which is on one side fitted with a female DB9 connector, and on the other side with an RJ11 jack. Setup is the same when multiple meters are interconnected via cables CBL03, except that all meters now need to be set to a different digital address via their front panel. Please contact Mosaic Industries if you need these custom configurations.

If your computer does not have an RS-232 serial port, low cost USB-to-RS-232 serial cables are available; contact Mosaic Industries for details. Now you can stock just one adapter to fill all your legacy "RS" serial interfacing plus provide a low level TTL control interface. Below you will see a cabling example for one master and two slaves in a full-duplex and a half-duplex situation. The solution is provided by the Laureate DIN rail mounted breakout board, which provides two RJ11 jacks with six screw clamp terminals all wired in parallel. 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. This provides high noise immunity and allows distances up to 4,000 ft (1200 meters). The RS485 protocol uses differential data signals for improved noise immunity; thus RS485 can communicate over greater distances than RS232. The Serial 2 port is dedicated to RS232 communications at up to 4800 baud. The maximum sustainable baud rate on the secondary serial port is 4800 baud. Finally, for master devices, the SPR1 and SPR0 bits determine the baud rate at which data is exchanged.

The Serial 1 port can be configured for either RS232 or RS485 communications at up to 19200 baud. A jumper, J3, configures the primary serial port for either RS232 or RS485 operation. We can gain insight into the operation of the RS232 protocol by examining the signal connections used for the primary serial port in Table 9 6. The transmit and receive data signals carry the messages being communicated between the QScreen Controller and the PC or terminal. In this case, cable connections must be made to Serial 1 at pins 5 and 6 of the 10-pin Serial Header or pins 7 and 8 on the 24-pin Field Header. The primary and secondary serial communications ports are accessible through the QScreen's 10 pin, dual row Serial Header (H5) which is typically not installed, the 24 pin, dual row Field Header (H3), and through the individual DB-9 Serial 1 and Serial 2 connectors. What are the differences between RS485 and RS422 protocols?