What Is Rs485 Cable - Overview

The SPI control register, SPCR, contains 8 bits which must be initialized for proper control of the QVGA Controller’s SPI (M68HC11 Reference Manual, p.8-7). 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. 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 (M68HC11 Reference Manual, p.8-3). If the 68HC11 is initialized as a master (by setting the MSTR bit in the SPCR control register as explained below) then bit 5 of the Port D data direction register (DDRD) determines whether /SS is an input or an output. Clearing the MSTR bit in the SPCR control register automatically configures the /SS (slave select) pin as an input. Any of these conditions may generate an interrupt if the SPIE (SPI interrupt enable) bit in the SPCR control register is set. Initializing the 68HC11 as a slave (by clearing the MSTR bit in the SPCR control register as explained below) automatically configures the /SS pin as an input.

If the 68HC11 is initialized as a master by setting the MSTR bit, then bit 5 of the Port D data direction register (PORTD.DIRECTION) determines whether /SS is an input or an output. Pre-coded device drivers configure the SPI for a standard data format, and routines defined in this chapter make it easy to customize a data format and baud rate for your application. The rate of data transmission is expressed in bits per second, or baud. For example, at 4800 baud (bits per second), each bit lasts about 200 microseconds (µs), and if communications are full duplex (e.g., if the QScreen Controller echoes each incoming character), then there is a serial interrupt every 100 µs or so. For example, at 4800 baud (bits per second), each bit lasts about 200 microseconds (µs), and if communications are full duplex (e.g., if the QVGA Controller echoes each incoming character), what is rs485 cable then there is a serial interrupt every 100 µs or so. The maximum sustainable baud rate on the secondary serial port is 4800 baud. While the default baud rate of the primary serial port is 9600 baud, you can speed your communications and download times appreciably by switching to a faster baud rate.

You can use the QED Board’s RS485 link to create such a multi-drop serial network. It provides a convenient means of connecting the QVGA Controller to a variety of peripheral devices, including analog to digital and digital to analog converters, real time clocks, and other computers which use high speed communication. Connecting a standard full duplex link RS232 between two computers is the same as with a standard RS232 link, with the TxD (transmitter output) of each computer connected to the RxD (receiver input) of the other computer. It is like the Universal Serial Bus (USB) or ethernet that we can find in many of our modern computers. This converter converts a USB port to not only RS485 but also RS232 and TTL, making it more versatile. Clueing in from its name, this is a USB to RS485 converter with industrial-grade features. The primary serial channel can operate at standard speeds up to 19200 baud and can be configured for either RS232 (the default) or RS485 operation. If the /SS pin of the master is an output, it can be controlled independently of the SPI system.

Also, in the diagram, the master QVGA Controller’s /SS (slave select) is configured as an output. If you do this now, remember to move the QVGA Controller’s serial connector back to Serial Port 1, and to change the terminal’s baud rate back to 9600 baud using the "Communications" item under the terminal’s "Settings" menu. The new baud rate takes effect upon the next reset or restart. The foreword to the standard references The Telecommunications Systems Bulletin TSB-89 which contains application guidelines, including data signaling rate vs. If the /SS input to a slave is active (low), the slave transfers data in response to the SCK clock input that is initiated by the master. It is a LoRaWAN converter that converts those sensors that are not LoRa-powered into LoRa-enabled sensors and therefore transfers data through the LoRaWAN protocol. The /SS (active-low slave select) signal enables data transfers by slave devices when it is active low.