Datasheet

Table Of Contents
Section 13 Serial Communication Interface
REJ09B0140-0900 Rev. 9.00 Page 443 of 846
Sep 16, 2010
H8S/2215 Group
No
<End>
[1]
Yes
Initialization
Start transmission
Read TDRE flag in SSR [2]
Write transmit data to TDR and
clear TDRE flag in SSR to 0
No
Yes
No
Yes
Read TEND flag in SSR
[3]
Clear TE bit in SCR to 0
TDRE = 1
All data transmitted?
TEND = 1
[1] SCI initialization:
The TxD pin is automatically designated as
the transmit data output pin.
[2] SCI status check and transmit data write:
Read SSR and check that the TDRE flag is
set to 1, then write transmit data to TDR
and clear the TDRE flag to 0.
[3] Serial transmission continuation procedure:
To continue serial transmission, be sure to
read 1 from the TDRE flag to confirm that
writing is possible, then write data to TDR,
and then clear the TDRE flag to 0.
Checking and clearing of the TDRE flag is
automatic when the DMAC or the DTC* is
activated by a transmit data empty interrupt
(TXI) request and data is written to TDR.
Note: * Checking and clearing of the
TDRE flag are performed
automatically by the DTC when
the DTC’s DISEL bit is cleared
to 0 and the transfer counter
value is not 0. Consequently, it
is necessary to use the CPU to
clear the TDRE flag if DISEL is
set to 1 or if the transfer
counter value is 0.
Figure 13.21 Sample Serial Transmission Data Flowchart