Sci Initialization (Asynchronous Mode) - Hitachi H8S/2378, H8S/2378R Series Hardware Manual

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. 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.
Start of initialization
Clear TE and RE bits in SCR to 0
Set CKE1 and CKE0 bits in SCR
(TE, RE bits 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 completed>
Rev. 1.0, 09/01, page 662 of 904
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
[1]
immediately after SCR settings are
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
[3]
an external clock 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.
Setting the TE and RE bits enables
the TxD and RxD pins to be used.
[4]