Hitachi H8/3664 Hardware Manual page 306

SCI3 operates as follows when transmitting data.
SCI3 monitors bit TDRE in SSR, and when it is cleared to 0, recognizes that data has been written
to TDR and transfers data from TDR to TSR. It then sets bit TDRE to 1 and starts transmitting. If
bit TIE in SCR3 is set to 1 at this time, a TXI request is made.
Serial data is transmitted from the TXD pin using the relevant data transfer format in table 14.11.
When the stop bit is sent, SCI3 checks bit TDRE. If bit TDRE is cleared to 0, SCI3 transfers data
from TDR to TSR, and when the stop bit has been sent, starts transmission of the next frame. If bit
TDRE is set to 1, bit TEND in SSR is set to 1, and the mark state, in which 1s are transmitted, is
established after the stop bit has been sent. If bit TEIE in SCR3 is set to 1 at this time, a TEI
request is made.
Figure 14.18 shows an example of the operation when transmitting using the multiprocessor
format.
Start
bit
Serial
1 0
data
TDRE
TEND
LSI TXI request
operation
User
processing
Figure 14.18 Example of Operation when Transmitting using Multiprocessor Format
Multiprocessor Receiving: Figure 14.19 shows an example of a flowchart for multiprocessor data
reception. This procedure should be followed for multiprocessor data reception after initializing
SCI3.
290
Transmit
data
D0 D1 D7
1 frame
TDRE
cleared to 0
Data written
to TDR
(8-Bit Data, Multiprocessor Bit, 1 Stop Bit)
Stop Start
bit bit
MPB
0/1 1 0 D0
TXI request
Transmit
data
MPB
D1 D7 0/1
1 frame
Stop Mark
bit state
1 1
TEI request