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Details of Pins in Block Diagram
The actual pin names and interrupt request numbers used in the UART1 are as follows:
SIN1 pin: P40/SIN1
SCK1 pin: P41/SCK1
SOT1 pin: P42/SOT1
Transmit interrupt number 1: #38 (26
Receive interrupt number 1: #37 (25
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Clock selector
The clock selector selects the transmit/receive clock from the dedicated baud rate generator, external input
clock, and internal clock (clock supplied from 16-bit reload timer).
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Reception control circuit
The receive controller is composed of receive bit counter, start bit detector and receive parity counter.The
receive bit counter counts the receive data, and outputs a receive interrupt request when reception of one
piece of data is completed.
The start bit detector detects the start bit from the serial input signal and writes the received data to the
serial input data register, on a bit-by-bit shift basis in accordance with the transfer rate.The receive parity
counter detects a parity bit in received data.
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Transmission control circuit
The transmit controller is composed of the transmit bit counter, transmit start circuit, and transmit parity
counter.The transmit bit counter counts the transmit data, and outputs a transmit interrupt request when
transmission of one piece of data is completed according to the set data length.The transmit start circuit
starts transmission when serial output data register (SODR1) is written.The transmit parity counter
generates the parity bit of the data transferred when parity is provided.
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Receive shift register
The receive shift register writes the receive data input from the SIN pin while shifting bit-by-bit, and when
the data reception is completed, it transfers the receive data to the serial input data register (SIDR1).
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Transmit shift register
Data written to SODR1 is transferred to the transmit shift register itself, and then the data is output to the
SOT pin while shifting bit-by-bit.
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CHAPTER 15 UART1
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