261
10.9 UART Interrupt Occurrence and Flag Setting Timing
Interrupt Flag Set Timing for Data Recepion in Mode 1
When the last stop bit is detected after data reception/transfe r is comp le ted, the ORE, FRE, and
RDRF flags are set to issue an interrupt request to the CPU. Since the length of data item s t hat
can be received is eight bits, the data at the last bit, bit 9, indicates an address or tha t 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)
Interrupt Flag Set Timing for Data Reception in Mode 2
When the last data item (D7) is detected after data recepti on/transfer is completed, the ORE
and RDRF flags are set to issue an interrupt request to the CP U. If ORE is active, th e 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