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Although the maximum standard baud rate of the primary serial port is 19200 baud, nonstandard baud rates of over 80 Kbaud can be attained by the 68HC11's on-chip UART and the onboard RS232 driver. The primary serial port, Serial1, is supported by the 68HC11's on-chip hardware UART (sometimes called a USART), and does not require interrupts to work properly. Because the software UART is interrupt based, competing interrupts that prevent timely servicing of the Serial2 interrupts can cause communications errors on the secondary serial channel. 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. The Serial2 channel is always configured for RS232 communications, and can sustain baud rates up to 4800 baud. This chapter describes those drivers, and presents code that makes it easy to configure the SPI for different data transfer rates and formats. The SPI can transfer data much more rapidly than an asynchronous serial link - its maximum rate is 2 Megabits/second. 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 one you choose depends on the specific device, or devices you will be connecting to.

If an interrupt service routine takes longer than 200 µs, then an entire serial bit will be missed, causing a communications error. In the middle of a character, each interrupt service routine takes about 35 µs. At the end of a received character, the service routine takes about 45 µs. 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. When the exchange is complete, the slave can again execute the Silence() routine to disable its transmitter and begin listening for its name. To ensure that no two devices drive the network at the same time, it is necessary that each slave device be able to disable it’s own RS-485 data transmitter.

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. Control and monitoring systems: A single pair of rs485 signal cable can connect up to 32 devices, with a signal transmission distance of up to 1200m. Therefore, using rs485 cables is an ideal choice for industrial control and monitoring systems, especially those with large-scale and high dispersion. At any given time, only the master and a single "active" slave communicate. In these distributed processing networks, a variety of machines and instruments work locally, but communicate and share data or resources with one another globally using a single serial link. RS485 main advantages as compared to other serial communication are tolerance to electrical noise, lengthy cable runs, multiple slaves in one connection, and fast data transmission speed. These advantages compared to other alternatives made RS485 popular and used in a widespread amount of instances. RS485 has many advantages over other standards, especially when it comes to applications in noisy industrial environments.

HD-SDI series delivers crystal clear mega pixel images without compression over coax. With RS232 well established and the need for faster communications and over longer distances, further standards beyond RS232 were introduced. Connecting analog instruments is very simple; you just need to connect the phase and neutral cables to the instrument. Choosing an analog instrument ensures good reading stability, due to the mechanical inertia of the needle and the fact that the reader immediately knows whether the instrument is operating normally or if the reading is out of range. The byte-sized messages are transmitted and received via the MOSI (master out/slave in) and MISO (master in/slave out) pins. You can find out more about the differences between RS485 and RS232 here. Designed for RS485 data connections. The data exchange format may be a line of ascii text. This section describes the QED-Forth routines that control the RS485 transceiver, and presents some ideas that may prove useful in designing a multi-drop data exchange protocol. RESOURCE and the access control functions GET() and RELEASE(). For the QScreen, /SS is not used for SPI communication because it is used to control the direction of the RS485 transceiver; you can use any digital I/O line as a /SS signal.

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