Rev. 1.00, 09/03, page 460 of 704
Wait
<Transfer start>
Start initialization
Set data transfer format in
SMR and SCMR
No
Yes
Set value in BRR
Clear TE and RE bits in SCR to 0
[2]
[3]
Set TE and RE bits in SCR to 1, and
set RIE, TIE, TEIE, and MPIE bits
[4]
1-bit interval elapsed?
Set CKE1 and CKE0 bits in SCR
(TE and RE bits are 0)
[1]
[1] Set the clock selection in SCR. Be sure
to clear bits RIE, TIE, TEIE, MPIE, TE,
and RE to 0.
[2] Set the data transfer format in SMR and
SCMR.
[3] Write a value corresponding to the bit
rate to BRR. This step is not necessary
if 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.
Note: In simultaneous transmit and receive operations, the TE and RE bits should both be cleared
to 0 or set to 1 simultaneously.
Figure 16.15 Sample SCI Initialization Flowchart
16.6.3
Serial Data Transmission (Clocked Synchronous Mode)
Figure 16.16 shows an example of SCI operation for transmission in clocked synchronous mode.
In serial transmission, the SCI operates as described below.
1. The SCI monitors the TDRE flag in SSR, and if it is 0, recognizes that data has been written to
TDR, and transfers the data from TDR to TSR.
2. After transferring data from TDR to TSR, the SCI sets the TDRE flag to 1 and starts
transmission. If the TIE bit in SCR is set to 1 at this time, a TXI interrupt request is generated.
If the TXI interrupt routine writes the next transmit data to TDR before transmission of the
current transmit data has finished, continuous transmission can be enabled.
3. 8-bit data is output from the TxD pin synchronized with the output clock when output clock
mode has been specified and synchronized with the input clock when use of an external clock
has been specified.
4. The SCI checks the TDRE flag at the timing for sending the last bit.
Содержание H8S/2437
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