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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. Note that clearing RE to 0, however, does not initialize the RDRF, PER, and
ORE flags, or RDR, which retain their previous contents.
Figure 13.15 shows a sample flowchart for initializing the SCI.
Start of initialization
Clear TE and RE bits to 0 in SCR
Set RIE, TIE, TEIE, 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?
Yes
Set TE or RE bit to 1 in SCR
Set RIE, TIE, TEIE, and MPIE
bits as necessary
<Start transmitting or receiving>
Figure 13.15 Sample Flowchart for SCI Initialization
(1)
(2)
(3)
Wait
Yes
(4)
Section 13 Serial Communication Interface
(1)
Set 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.* 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.
Note: *
In simultaneous transmitting and receiving,
the TE and RE bits should be cleared to 0 or
set to 1 simultaneously.
Rev. 4.00 Jan 26, 2006 page 527 of 938
REJ09B0276-0400
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