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Bit 7—Transmit Data Register Empty (TDRE): Indicates that the SCI has loaded transmit
data from TDR into TSR and the next serial transmit data can be written in TDR.
Bit 7
TDRE
Description
0
TDR contains valid transmit data
[Clearing conditions]
Software reads TDRE while it is set to 1, then writes 0.
1
TDR does not contain valid transmit data
[Setting conditions]
The chip is reset or enters standby mode.
The TE bit in SCR is cleared to 0.
TDR contents are loaded into TSR, so new data can be written in TDR.
Bit 6—Receive Data Register Full (RDRF): Indicates that RDR contains new receive data.
Bit 6
RDRF
Description
0
RDR does not contain new receive data
[Clearing conditions]
The chip is reset or enters standby mode.
Software reads RDRF while it is set to 1, then writes 0.
The DMAC reads data from RDR.
1
RDR contains new receive data
[Setting condition]
When serial data is received normally and transferred from RSR to RDR.
Note: The RDR contents and RDRF flag are not affected by detection of receive errors or by
clearing of the RE bit to 0 in SCR. They retain their previous values. If the RDRF flag is
still set to 1 when reception of the next data ends, an overrun error occurs and receive
data is lost.
302
(Initial value)
(Initial value)
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