Three Ways You Can Reinvent Rs485 Cable Without Looking Like An Amateur > 자유게시판

Also, several non-serial interrupts can stack up; if they have higher priority than the serial interrupts, they will be serviced before the Serial2 interrupt routine, and again a serial input or output bit may be lost. By polling the Port A pin or by setting up an interrupt service routine, you can configure the QScreen to ignore the SCK input when /SS is high and keep MISO in a high-impedance state so that it does not interfere with the SPI bus. Alternatively, the if the SPI interrupts are enabled, the SPI interrupt handler determines what caused the interrupt by reading the SPSR register to see which of the three status bits is set. Then reading the data that was received (by reading the SPDR) or initiating a new data transfer (by writing to the SPDR) automatically clears the SPIF flag. Then the programming software can be used to complete the normal communication with the PLC. HP is a company that makes and market particular hardware / software for speciallist application.

If your application requires use of the secondary serial port as well as other interrupt routines, the key is to keep the interrupt service routines short and fast. If an interrupt service routine takes longer than 200 µs, then an entire serial bit will be missed, causing a communications error. The Silence() routine searches the incoming serial characters for a pre-determined keyword (for example, the ascii "name" of this particular slave). If more than one slave tried to drive the transmit line simultaneously, their serial drivers would fight with each other for control of the bus. 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. Although data byte transfers are easily executed once the network has been wired and configured properly, a carefully executed software protocol may be required to ensure data integrity. Because the requirements of every multi-drop application are so unique, it is difficult to specify or design a software protocol that meets everyone’s needs. We have built sophisticated instruments using the QScreen Controller that operate very reliably using multiple interrupts in addition to the software UART. These drivers are usually included in the programming software on CD-ROM And for the specific installation steps, please refer to the instruction files on the CD-ROM drivers, and details are not necessarily listed here.

TSX08PRGCAB (also known as TSXPCX1031) is the programming cable which is provide connection and the RS485 signal converter through the RS232 serial interface. A ground connection is also necessary to ensure that the communicating devices have a common voltage reference. 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. The CPHA bit determines whether data is valid on the leading or trailing edge of the clock. The BufferToSPI() function implements fast data transfer from a specified buffer in the controller’s memory to an SPI device. Any of these conditions may generate an interrupt if the SPIE (SPI interrupt enable) bit in the SPCR control register is set. SPIE is a local interrupt mask that allows an interrupt to be recognized when an SPI data transfer has completed, or if a write collision or mode fault is detected.

This chapter describes those drivers, and presents code that makes it easy to configure the SPI for different data transfer rates and formats. Once the data has been exchanged, a flag bit in the SPSR status register is set to indicate that the transfer is complete. There are three flag bits implemented in the SPSR (SPI status register). If you are using the QScreen as a master device, each external SPI device will require a separate select line (/SS). 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. RS232/RS485 interface cable for Schneider PLC programming,3 meters,with master/slave switch,used for programming communication or other communication such as MODBUS. RS485 communication cable, then connect back of the DVR panel. To use a QScreen as a slave in a multi-drop network, simply define a word, (named Silence(void), for example) that when executed calls 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.

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