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8.3.3 Clocked Synchronous Operation
(1) Overview: In clocked synchronous mode, the SCI transmits and receives data in
synchronization with clock pulses. This mode is suitable for high-speed serial communication.
The SCI transmitter and receiver share the same clock but are otherwise independent, so full duplex
communication is possible. The transmitter and receiver are also double buffered, so continuous
transmitting or receiving is possible by reading or writing data while transmitting or receiving is in
progress.
Figure 8-12 shows the general format in clocked synchronous serial communication.
*
Serial clock
Data
Don't care
Note:
*
High except in continuous transmitting or receiving
Figure 8-12. Data Format in Clocked Synchronous Communication
In clocked synchronous serial communication, each data bit is sent on the communication line from
one falling edge of the serial clock to the next. Data are received in synchronization with the rising
edge of the serial clock.
In each character, the serial data bits are transmitted in order from LSB (first) to MSB (last). After
output of the MSB, the communication line remains in the state of the MSB until the next falling
edge of the serial clock.
One unit (character or frame) of serial data
LSB
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
197
*
MSB
Bit 6
Bit 7
Don't care
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