The Asynchronous Serial Interfaces can be seen in mostly in long distance applications and are a perfect fit for the stable communication. On the transmitter side , there is a shifting of parallel data onto the serial line using its own clock. Also it adds the start, stop and parity check bits.
On the receiver side, the receiver extracts the data using its own clock and convert the serial data back to the parallel form after stripping off the start, stop, and parity bits. Apart from Clock Synchronization there are certain things to remember when transferring data serially such as Baud Rate, Data bit selection Framing , Synchronisation and error checking.
Baud Rate: Baud rate is rate at which the data is transferred between the transmitter and receiver in the form of bits per second bps. The most commonly used baud rate is But there are other selection of baud rate such as , , , , The more the baud rate will be fats the data will be transferred at a time.
Also for the data communication the baud rate has to be same for both transmitter and receiver. Framing: Framing is referred to the number of data bits to be sent from transmitter to receiver. The number of data bits differs in case of application. Most of the application uses 8 bits as the standard data bits but it can be selected as 5, 6 or 7 bits also.
Synchronisation: Synchronization Bits are important to select a chunk of data. It tells the start and end of the data bits.
The transmitter will set start and stop bits to the data frame and the receiver will identify it accordingly and do the further processing. Error Control: The error control plays an important role while serial communication as there are many factors which affects and adds the noise in the serial communication. To get rid of this error the parity bits are used where parity will check for even and odd parity.
Protocol is just like a common language that system uses to understand the data. As described above, the serial communication protocol is divided into types i. Synchronous and Asynchronous. Now the both will be discuss in detail. Also these are the widely used protocols in major applications. In SPI, separate wires are required for data and clock line.
Also the clock is not included in the data stream and must be furnished as a separate signal. The SPI may be configured either as master or as a slave. So it needs 6 wires to send and receive data from slave or master. Theoretically, the SPI can have unlimited number of slaves. The data communication is configured in SPI registers.
The SPI can deliver up to 10Mbps of speed and is ideal for high speed data communication. Both the lines must be connected to a positive supply using a pull up resistor. I2C can deliver speed up to Kbps and it uses 10 bit or 7 bit addressing system to target a specific device on the i2c bus so it can connect up to devices.
It has limited length communication and is ideal for onboard communication. I2C networks are easy to setup since it uses only two wires and new devices can simply be connected to the two common I2C bus lines. A maximum of peripherals can be connected to a single USB host controller.
USB acts as "plug and play" device. The USB are used in almost devices such as keyboards, printers, media devices, cameras, scanners and mouse.
Each product that can be used in a lighting system has an icon so that you can quickly see which system it is designed to work in. David Bell is the founder of Vesternet. Access Technical Experts. A 2-wire system includes two wires - Live and Switched Live. Are all the wires connected to the switch? Do all the wires have a brown sleeve on them? If the answer is YES to either of these points, you have a 2-wire system Do you have two blue, black or grey wires going to a connector block?
If so you MAY have a 3-wire system, but you should confirm this with a voltage meter or consult a qualified electrician. Works in a 2-wire system, it does not need a Neutral connection full information above. Works in a 3-wire system, a Neutral is required full information above.
Last Update :. About the Author Find us on E-mail. Therefore it is important to qualify whether it is the transmitter or the control system that is to be wired in a specific configuration. For the purposes for this guidance note it is assumed that both the transmitter and the remote control panel require a 24Vdc supply.
The mA signal flows through the 24V dc line and the signal line to the controller. The mA signal flows through the 0V dc line and the signal line to the controller. The transmitter and control panel use separate power supplies. The mA signal flows through two separate cable cores between the transmitter and control panel.
This configuration supplies power and mA signal over a two wire loop connection between the transmitter and the control panel. Not all transmitters can be wired in this format and must be specifically designed to accommodate this configuration. Sub 4mA status signalling is limited due the reduced range of mA available between fault and a zero reading.
Not suitable for power hungry transmitters, e. You can also follow us on Facebook and Twitter to receive daily updates. One thing I noticed was not mentioned in the wiring of the loops. The limitations and effects of circuit impedance of the loop. I see issues on a regular basis where technicians and engineers have issues with their current loops functioning properly. I have them check the circuit impedance and this is usually the issue, and they have to add a resistor either in parallel or series depending on the requirements.
As per my understanding, the most common used configuration of modern mA transmitters is Two Wire Loop Powered Transmitters. Just two cable cores are required to connect from the transmitter to control system. Such loop powered transmitters with HART are very popular in the transmitter market and able to cover lots of commonly used process measurement variables such as Pressure, Temperature, Flow, Level and simple Quality pH, conductivity, moisture, etc.
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