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CHAPTER 13 UART
13.6.1 Transmission Operations (Operating Mode 0, 1, 2, and 3)
When writing data to be transmitted into the SODR register after reading the SSD
register sends the data written into the SODR register to the transmission shift register,
parallel-serial conversion then starts. The data converted is output at the serial data
output pin from the lowest bit in sequence (with LSB first). When the next data becomes
writable, "1" is set to the TDRE bit, then an interrupt request to the CPU is generated if
the transmission interrupt is allowed (SSD: TIE = 1).
■ Transmission Operations in Operating Mode is 0, 1, 2, or 3
Figure 13.6-3 shows the transmission operations when operating mode is 1, parity is not used, and the
number of stop bits is "1".
Figure 13.6-3 Transmission Operations in Operating Mode 0, 1, 2, or 3
STOPSTART START
01234567
SSD read
SODR write
(interrupt processing
routine)
Transmission interrupt
TDRE
Data transmitted
Transmission buffer full
Sent to the transmission shift register
Sent to the transmission shift register