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What serial interface is built in a microcontroller?

Latest Updated:04/01/2006

Question:

What serial interface is built in a microcontroller?

Answer:

The following serial interfaces are provided to a microcontroller.
Of these, (1) to (3) are mainly used.
(1) can be connected to RS-232C used for PCs, by converting signal levels.
(2) and (3) are mainly used for on-board connection of microcontrollers and a microcontroller and an external EEPROM.

(1) UART (Universal Asynchronous Receiver and Transmitter)
This is the most commonly used interface.
It can transfer data of 7 or 8 bits and can check errors by using parity.
In addition to this interface, some microcontrollers support
- Infrared communication function
- LIN (Local Interconnect Network) interface function
Some UART interfaces have a function to successively transmit multiple data, in addition to transmitting individual data.
(Also refer to "Selecting serial I/F" and "Basic operation of start-stop synchronization".)

(2) Three-wire serial interface
This interface uses three signal lines, a serial clock line and two data lines, and can transfer 8-bit data bidirectionally at relatively high speeds.
Data can be selectively transferred starting from the lowest or highest bit.
Some microcontrollers also support
- Functions compatible with SPI (Serial Peripheral Interface)
- Functions to transfer multiple data
(Also refer to "Selecting serial I/F" and "Basic operation of three-wire serial communication".)

(3) I2C bus interface
This interface can communicate with two or more units, using two signal lines and in bus format.
Some types of this interface support a single master, while others support multiple masters (most of the latest devices support multiple masters).
(Also refer to "Selecting serial I/F" and "I2C bus".)

(4) SMB (System Management Bus)
This interface uses a bus using two signal lines, such as the I2C bus, for communication, and, depending on the setting, is compatible with I2C.
Some devices are equipped with this interface.

(5) CAN (Controller Area Network)
This bus is mainly used in automobiles.
Several types of interfaces are available depending on what standard is supported.

(6) IE-Bus
This is also mainly used in automobiles and covers transfer rates lower than those of CAN.
An IE-bus controller provided to a microcontroller is usually of sub-set version.

Suitable Products
RL78 Family
78K Family
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