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10.9 UART Interrupt Occurrence and Flag Setting Timing
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Interrupt Flag Set Timing for Data Recepion in Mode 1
When the last stop bit is detected after data reception/transfer is completed, the ORE, FRE, and
RDRF flags are set to issue an interrupt request to the CPU. Since the length of data items that
can be received is eight bits, the data at the last bit, bit 9, indicates an address or that data is
invalid. If ORE or FRE is active, the SIDR data is invalid.
Figure 10.9-2 ORE, FRE, and RDRF Set Timing (Mode 1)
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Interrupt Flag Set Timing for Data Reception in Mode 2
When the last data item (D7) is detected after data reception/transfer is completed, the ORE
and RDRF flags are set to issue an interrupt request to the CPU. If ORE is active, the SIDR
data is invalid.
Figure 10.9-3 ORE and RDRF Set Timing (Mode 2)
D7 Stop
ORE, FRE
RDRF
Reception interrupt
Data
Address/
data
D5 D6 D7
ORE
RDRF
Reception interrupt
Data