Hitachi H8S/2338 Series Hardware Manual page 448

• Serial data transmission (synchronous mode)
Figure 11-16 shows a sample flowchart for serial transmission.
The following procedure should be used for serial data transmission.
Initialization
Start of transmission
Read TDRE flag in SSR
TDRE = 1?
Write transmit data to TDR and
clear TDRE flag in SSR to 0
All data transmitted?
Read TEND flag in SSR
TEND = 1?
Clear TE bit in SCR to 0
<End>
No
Yes
No
Yes
No
Yes
Figure 11-16 Sample Serial Transmission Flowchart
[1] SCI initialization:
[1]
The TxD pin is automatically
designated as the transmit data output
pin.
[2] SCI status check and transmit data
[2]
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
[3]
TDRE flag to 0.
Checking and clearing of the TDRE
flag is automatic when the DMAC or
DTC is activated by a transmit-data-
empty interrupt (TXI) request and data
is written to TDR.
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