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 10-14.
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 bit is set to 1, 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 10-23 shows an example of the operation when transmitting using the multiprocessor
format.
Start
bit
Transmit
data
Stop Start
bit bit
Transmit
data
Stop
bit
Mark
state
MPB
MPB
Serial
data
1
0
D0 D1
D7 0/1
1
0
D0 D1
1 frame
D7 0/1
1
1
1 frame
TDRE
TEND
LSI
operation
TXI request TDRE
cleared to 0
TXI request
TEI request
User
processing
Data written
to TDR
Figure 10-23 Example of Operation when Transmitting using Multiprocessor Format
(8-bit data, multiprocessor bit, 1 stop bit)
•
Multiprocessor receiving
Figure 10-24 shows an example of a flowchart for multiprocessor data reception. This procedure
should be followed for multiprocessor data reception after initializing SCI3.
314
ETC [ ETC ]
