Fujitsu MB90460 Series Hardware Manual page 490

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Clock selector
The clock selector selects the dedicated baud rate generator, external input clock, or internal clock (clock
supplied from the 16-bit reload timer) as the transmitting and receiving clocks.
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Reception control circuit
The reception control circuit consists of a received bit counter, start bit detection circuit, and received
parity counter. The received bit counter counts receive data bits. When reception of one data item for the
specified data length is complete, the received bit counter generates a reception interrupt request. The start
bit detection circuit detects start bits from the serial input signal. When the circuit detects a start bit, it
writes data in the SIDR1 register by shifting at the specified transfer rate. The received parity counter
calculates the parity of the receive data.
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Transmission control circuit
The transmission control circuit consists of a transmission bit counter, transmission start circuit, and
transmission parity counter. The transmission bit counter counts transmission data bits. When transmission
of one data item of the specified data length is complete, the transmission bit counter generates a
transmission interrupt request. The transmission start circuit starts transmission when data is written to
SODR0/SODR1. The transmission parity counter generates a parity bit for data to be transmitted when
parity is enabled.
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Reception shift register
The reception shift register fetches receive data input from the SIN pin, shifting the data bit by bit. When
reception is complete, the reception shift register transfers receive data to the SIDR0/SIDR1 register.
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Transmission shift register
The transmission shift register transfers data written to the SODR0/SODR1 register to itself and outputs the
data to the SOT pin, shifting the data bit by bit.
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Mode control register 1 (SMC0/SMC1)
This register performs the following operations:
• Selecting a UART operation mode
• Selecting a clock input source
• Setting up the dedicated baud rate generator
• Selecting a clock rate (clock division value) when using the dedicated baud rate generator
• Specifying whether to enable serial data output to the corresponding pin
• Specifying whether to enable clock output to the corresponding pin
CHAPTER 17 UART
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