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. These steps greatly reduce the chance that the communicating devices might be damaged by contention on the SPI bus. Any of these conditions may generate an interrupt if the SPIE (SPI interrupt enable) bit in the SPCR control register is set. The SPIE bit in the SPCR (SPI control register) enables SPI interrupt handling. If the programmer has enabled the local interrupt mask for the SPI, an interrupt is recognized at this point. The configuration and specifications of RS485 make it faster and extend the range of data transmission. 12 V, i.e. ±7 V on top of the 0-5 V signal range. The RS485 communication interface allows the slave unit (i.e. control module) to be interrogated and some options programmed by a remote computer. The RS485 protocol used on Monicon's controllers is designed for simplicity and reliability. The simplicity of the wiring makes installation and maintenance easier, contributing to cost-effective and efficient communication network setups. RS232/485 TO ETH, check whether the RS232/RS485 wiring is correct or not.
RS-232 is a simple serial communication standard in which one bit of data is transmitted at a time over a serial cable at the relatively slow rate of up to 20K bits/second and distances up to 50-ft. By specifying the voltage, signaling, pin wiring and control data between a host device and a peripheral, the RS-232 standard ensured that devices from different manufacturers could communicate with each other. Although the devices would share the same network, communications would only be understandable by members of the same group. In general, all devices on a network should use the same phase, polarity, and baud rate clock signal. The one you choose depends on the specific device, or devices you will be connecting to. This setting is only relevant for the master device, as it is the master’s clock which drives the transfer. Transmissions are always initiated by the master device, and consist of an exchange of bytes. Once the bytes have been exchanged, the master may write a new byte to initiate another byte exchange. Once the data has been exchanged, a flag bit in the SPSR status register is set to indicate that the transfer is complete. The WCOL flag is set when a write collision occurs.
Thus, resetting the SPIF flag is very simple. In this section we will consider the most general and simple configurations. There are many possible configurations of master/slave networks. In some cases, however, a sophisticated network may have device groups on a network that use different clock configurations. However, the length can be extended considerably with a trade-off with slower data rates. 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. Setting the MSTR bit initializes the QScreen as a master, and clearing the MSTR bit initializes it as a slave. The DWOM bit determines whether Port D needs pull-up resistors; it should be set to 0. The MSTR bit determines whether the device is a master or slave. The status of a device as master or slave determines how the various pins must be configured.
It is important to note that when the CPHA bit is 0, the /SS line must be de-asserted and re-asserted between each successive data byte exchange (68HC11 Reference Manual, Section 8.3.2). If the CPHA bit is 1, the /SS line may be tied low between successive transfers. Any required SPI output signals must be configured as outputs, either by calling InitSPI() or by setting the appropriate bits in the Port D data direction register DDRD. At the maximum length of 15 meters (50 feet), an RS-232 port will support a data rates up to 20 Kbps. 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. Remember that the /SS is active low so to select a device you need to set the pin low; otherwise the pin should idle high. Even though the MOSI pin is not connected to anything, the master initiates a transmission using a "dummy" byte. If the /SS pin of the master is an input and if a low input level is detected, the processor sets the MODF bit in the SPI status register a "mode fault" condition.
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