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Why are double channels used in UART?

Latest Updated:02/01/2009

Question:

Although it is possible to transmit and receive by single channel with 3-wire serial I/O mode and simplified I2C, why are double channels used in UART?

Answer:

(1) I2C
transmitting and receiving are not doing at the same time (half-duplex communication), so channel (shift register) is enough by 1.

(2) 3-wire serial I/O mode
It is possible to transmit and receive at the same time (full-duplex communication). Master and slave are operating using with same clock timing, so channel (shift register) is enough by 1.

(3) UART
It is possible to transmit and receive at the same time (full-duplex communication). transmitting and receiving are operating individually, so channel (shift register) is required both for transmitting and receiving.
Suitable Products
RL78 Family
78K0R/Kx3