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Transmitting and Receiving Data
SCI Initialization (Synchronous Mode): Before transmitting or receiving, clear the TE and RE
bits to 0 in SCR, then initialize the SCI as follows.
When changing the communication mode or format, always clear the TE and RE bits to 0 before
following the procedure given below. Clearing the TE bit to 0 sets the TDRE flag to 1 and
initializes TSR. Clearing the RE bit to 0, however, does not initialize the RDRF, PER, FER, and
ORE flags and RDR, which retain their previous contents.
Figure 11-15 shows a sample flowchart for initializing the SCI.
Start of initialization
Clear TE and RE
bits to 0 in SCR
Set CKE1 and CKE0 bits in
SCR (leaving TE and RE
bits cleared to 0)
Select communication
format in SMR
Set value in BRR
1 bit interval
elapsed?
Yes
Set TE or RE to 1 in SCR
Set RIE, TIE, and TEIE
bits as necessary
Start transmitting or receiving
1
Note: In simultaneous transmitting and receiving, the TE and RE
2
3
Wait
No
4
Figure 11-15 Sample Flowchart for SCI Initialization
1.
Select the clock source in SCR. Clear the RIE, TIE, TEIE,
MPIE, TE, and RE bits to 0.
2.
Select the communication format in SMR.
3.
Write the value corresponding to the bit rate in BRR.
This step is not necessary when an external clock is used.
4.
Wait for at least the interval required to transmit or receive
one bit, then set the TE or RE bit to 1 in SCR. Also set
the RIE, TIE, and TEIE bits as necessary.
Setting the TE or RE bit enables the SCI to use the
TxD or RxD pin.
bits should be cleared to 0 or set to 1 simultaneously.
369
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