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Section 15 Serial Communication Interface (SCI)
15.4.4
SCI Initialization (Asynchronous Mode)
Before transmitting and receiving data, you should first clear the TE and RE bits in SCR to 0, then
initialize the SCI as shown in figure 15.5. When the operating mode, transfer format, etc., is
changed, the TE and RE bits must be cleared to 0 before making the change using the following
procedure. When the TE bit is cleared to 0, the TDRE flag in SSR is set to 1. Note that clearing
the RE bit to 0 does not initialize the contents of the RDRF, PER, FER, and ORER flags in SSR,
or the contents of RDR. When the external clock is used in asynchronous mode, the clock must be
supplied even during initialization.
Start initialization
Clear TE and RE bits in SCR to 0
Set CKE1 and CKE0 bits in SCR
(TE and RE bits are 0)
Set data transfer format in
SMR and SCMR
Set value in BRR
1-bit interval elapsed?
Set TE and RE bits in
SCR to 1, and set RIE, TIE, TEIE,
and MPIE bits
<Initialization completion>
Rev. 1.00 Apr. 28, 2008 Page 428 of 994
REJ09B0452-0100
Wait
No
Yes
Figure 15.5 Sample SCI Initialization Flowchart
[1]
Set the clock selection in SCR.
Be sure to clear bits RIE, TIE, TEIE, and
MPIE, and bits TE and RE, to 0.
When the clock is selected in
asynchronous mode, it is output
immediately after SCR settings are
[1]
made.
[2]
Set the data transfer format in SMR and
SCMR.
[2]
[3]
Write a value corresponding to the bit
rate to BRR. Not necessary if an
external clock is used.
[3]
[4]
Wait at least one bit interval, then set the
TE bit or RE bit in SCR to 1. Also set
the RIE, TIE, TEIE, and MPIE bits.
Setting the TE and RE bits enables the
TxD and RxD pins to be used.
[4]
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