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Transmitting and Receiving Data:
• SCI Initialization (Synchronous Mode): Before transmitting or receiving data, 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 TE to 0 sets the TDRE flag to 1 and
initializes TSR. Clearing RE to 0, however, does not initialize the RDRF, PER, FER, and
ORER flags, or RDR, which retain their previous contents.
Figure 12.15 shows a sample flowchart for initializing the SCI.
Start of initialization
Clear TE and RE bits to 0 in SCR
Set RIE, TIE, MPIE, 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?
Set TE or RE bit to 1 in SCR
Set RIE, TIE, TEIE, and MPIE
bits as necessary
<Start transmitting or receiving>
Note: * In simultaneous transmitting and receiving, the TE and RE bits should be cleared to 0
or set to 1 simultaneously.
358
Wait
Yes
Yes
Figure 12.15 Sample Flowchart for SCI Initialization
Set the clock source in SCR. Clear the
(1)
RIE, TIE, TEIE, MPIE, TE, and RE bits to
0.*
Set the communication format in SMR.
(2)
(1)
(3)
Write the value corresponding to the bit rate
in BRR.
This step is not necessary when an
external clock is used.
(2)
(4)
Wait for at least the interval required to
transmit or receive one bit, then set the TE
(3)
or RE bit to 1 in SCR.* Set the RIE, TIE,
TEIE, and MPIE bits as necessary.
Setting the TE or RE bit enables the SCI to
use the TxD or RxD pin.
(4)
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