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CHAPTER 13 UART
r 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 send data is written to the output data register (SODR0/SODR1).
The
transmission parity counter generates the parity bits for data when transmitting data with parity.
r Reception Shift Register
The reception shift register fetches receive data input from the SIN0/1 pin, shifting the data bit
by bit. When reception is complete, the reception shift register transfers receive data to the
SIDR0/1 register.
r Transmission Shift Register
The transmission shift register transfers data written to the SODR0/1 register to itself and
outputs the data to the SOT0/1 pin, shifting the data bit by bit.
r Mode Control Register (SMR0/1)
The mode register performs the operations of the operation mode setting, baud rate clock
setting, serial clock I/O control, and output enable setting of serial data to pins.
r Control Register (SCR0/1)
The control register performs the operations of the parity presence/absence setting, parity
setting, stop bit length/data length settings, frame data format setting in operation mode 1,
clearing of received error flag bits, and enable/disable setting of send/receive operations.
r Status Register (SSR0/1)
The status register performs the operations of status check for transmission/reception and
errors, transfer direction setting of serial data, and enable/disable setting of send/receive
interrupt requests.
r Input Data Register (SIDR0/1)
This register retains receive data.
r Output Data Register (SODR0/1)
This register sets transmission data. Data written to this register is converted to serial data and
output.