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CHAPTER 14 UART0
I Serial output data register 0 (SODR0)
W : Write only
X : Undefined
The serial output data register 0 (SODR0) is a data buffer register for transmitting serial data.
• When data to transmit is written to serial output data register 0 (SODR0) with transmission enabled
(SCR0: TXE = 1), the transmit data is transferred to the transmission shift register, converted to serial
data, then output from the serial data output pin (SOT0 pin).
• When the data length is seven bits, the data in upper one bit (D7) is invalid.
• The transmit data write flag (SSR0: TDRE) is cleared to 0 when data to transmit is written to serial
output data register 0 (SODR0).
• The transmit data write flag is set to "1" at completion of data transfer to the transmit shift register.
• The next data to transmit can be written when the transmit data write flag (SSR0: TDRE) contains
"1".Transmission interrupts occur while enabled (SSR0: TIE = 1).The succeeding transmit bit data
should be written with the transmit data write flag (SODR: TDRE) containing "1".
Note:
The serial output data register is a write-only register and the serial input data register is a
read-only register.Since the same address is allocated to the two registers, the values written
and read are different.Instructions, such as the INC/DEC instruction, which provide the read
modify write (RMW) operation cannot be used.
396
Figure 14.3-6 Serial output data register 0 (SODR0)
7
6
D7
D6
W
W
5
4
3
2
D5
D4
D3
D2
D1
W
W
W
W
W
1
bit0
Reset value
D0
XXXXXXXX
B
W
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