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It may be that only the byte sent from the master to the slave is meaningful; nevertheless, each device simultaneously transmits and receives one byte. The distinction between master and slave is an important one. The InitSPI() function provides a convenient way to initialize the SPI as the master at a 2MHz baud rate. This function cannot accept incoming data; consult its glossary entry for details. Consult their glossary entries for details. Once the data has been exchanged, a flag bit in the SPSR status register is set to indicate that the transfer is complete. After a data transfer is initiated by writing to the SPDR data register, the processor may poll the SPSR status register until the SPIF flag is set. Full-duplex mode is used when you need to be able to transmit and receive data at the same time. The DWOM bit (port D wired-or mode) should always be set to 0. Setting DWOM to 1 takes away the processor’s ability to pull the Port D signals high unless there is a pull-up resistor on each bit of the port. A mode fault occurs when the SPI senses that a multimaster conflict (MC68HC11F1 Technical Data Manual, p.8-7) exists on the network as explained above in connection with the /SS input.

The SPIF is set when a data transfer is complete, and is cleared by a read of the SPSR status register, followed by a read or write to the SPDR data register. The SPIE bit in the SPCR (SPI control register) enables SPI interrupt handling. The next section describes the registers that configure and control the QScreen Controller’s SPI. Consult the data sheets for any peripheral devices that you are interfacing to the SPI and, if a different configuration is needed, follow the instructions below to set up the appropriate SPI data transfer protocol. In recent years, advancements in RS485 cable technology have focused on improving data transfer speeds and increasing the efficiency of data transmission. The transmission speed of RS485 cables can vary depending on factors such as cable length, baud rate, and the quality of the cable itself. With careful design, many peripherals can communicate via the SPI, and powerful multi-processor systems can be linked using this high speed bus. The flexibility and power of the 68HC11’s serial peripheral interface supports high speed communication between the 68HC11 and other synchronous serial devices.

Depends what you mean by a serial cable - Fibre, Ethernet, RS232, RS485, RS422, USB, HDMI, SMPTE292 are all examples of serial communications media. Load Cell Systems bulk 4-conductor (2 twisted pair) with drain wire serial communications cable - RS232 or RS485, 0.353″ diameter PVC outer jacket. RS485 is in its design a different interface from RS232. RS485 cable is a type of communication cable commonly used in industrial settings for connecting devices in a network. 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. There is also the GSM version; especially useful when only one sensor is needed in a remote location where other types of transmission cannot be used. Regardless of the network, however, there are only four signals used: SCK provides a synchronized clock, MOSI and MISO signals are used for data transmission and reception, and /SS configures the QScreen as a master or slave device. Finally, for master devices, the SPR1 and SPR0 bits determine the baud rate at which data is exchanged.

The SCK pin’s synchronous clock signal has configurable phase, polarity and baud rate so that it can interface to a variety of synchronous serial devices. In general, all devices on a network should use the same phase, polarity, and baud rate clock signal. The clock’s polarity is controlled by a bit named CPOL (clock polarity) and its phase is controlled by CPHA (clock phase). To interface devices that support synchronized serial interfaces, but are not configurable like the QScreen, determine the device’s requirements for clock phase and polarity and configure the QScreen’s CPHA and CPOL accordingly. This automatically activates the SCK clock which synchronously transmits the data. The device that initiates a data transfer is the master, and all other devices on the network are slaves. Given a properly wired network and a properly configured SPCR control register, a master device may transmit a message by simply storing the byte to the SPDR data register. Data rates of 100Kbps can be achieved over distances of up to 1200 meters. LAPP UNITRONIC ® BUS LD FD P cables are built after the RS-422 and RS-485 standards and are robust solutions for transmitting data over long distances and noisy environments.