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CHAPTER 13 UART
Note:
The inside of UART is initialized when it is in synchronization transfer mode, asynchronous transfer
mode, external clock mode, or internal clock mode with the clock from the prescaler. Therefore, turn on
the PREN bit (PREN = 1) to enable operation of the prescaler before using the UART functions.
Table 13.4-4 Explanation of Functions of Each Bit in the Clock Divider Selection Register (UPC)
Bit name Description
bit7
to
bit4
Unused bits
• The values read out from these bits are undefined.
• Writing values into these bits does not affect any operation.
bit3
PREN:
UART prescaler
operation enable bit
• Enables/disables operation of the prescaler that creates the UART reference clock
by dividing the oscillation frequency.
• When this bit is "1", the UART prescaler supplies the reference clock that
corresponds to the frequency selected using the oscillation frequency selection bit
to the baud rate generator. When this bit is "0", the prescaler does not operate, thus
the internal baud rate generator cannot be used for data transfer or data receive
purposes.
bit2
to
bit0
PR2, PR1, PR0:
Clock divider selection
bits
• The UART prescaler supplies to the internal baud rate generator, the reference
clock that corresponds to the divider selected using these bits.