Datasheet

Section 13 Serial Communication Interface
REJ09B0140-0900 Rev. 9.00 Page 427 of 846
Sep 16, 2010
H8S/2215 Group
13.4.4 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 described in a sample flowchart in figure 13.9. When the operating mode, or
transfer format, is changed for example, 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 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, or the contents of RDR. When the external clock is used in asynchronous mode, the
clock must be supplied even during initialization.
Wait
<Initialization completion>
Start initialization
Set data transfer format in
SMR, SCMR, and SEMR
[1]
Set CKE1 and CKE0 bits in SCR
(TE, RE bits 0)
No
Yes
Set value in BRR
Clear TE and RE bits in SCR to 0
[2]
[3]
Note: * Set this bit while the RxD pin is 1. If
the RE bit is set to 1 while the RxD
pin is 0, the signal may erroneously
be recognized as a start bit.
Set TE and RE bits* in
SCR to 1, and set RIE, TIE, TEIE,
and MPIE bits
[4]
1-bit interval elapsed?
[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
made.
[2] Set the data transfer format in SMR,
SCMR, and SEMR.
[3] Write a value corresponding to the bit
rate to BRR. Not necessary if an external
clock or average transfer rate clock by
ACS2 to ACS0 is used.
[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.
Figure 13.9 Sample SCI Initialization Flowchart