HD64F2149 Datasheet, PDF (492/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

15.3.4 Operation in Synchronous Mode
In synchronous mode, data is transmitted or received in synchronization with clock pulses, making
it suitable for high-speed serial communication.
Inside the SCI, the transmitter and receiver are independent units, enabling full-duplex
communication by use of a common clock. Both the transmitter and the receiver also have a
double-buffered structure, so that data can be read or written during transmission or reception,
enabling continuous data transfer.
Figure 15.14 shows the general format for synchronous serial communication.
*
Serial
clock
Serial
data
Don’t care
LSB
Bit 0
One unit of transfer data (character or frame)
Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6
*
MSB
Bit 7
Don’t care
Note: * High except in continuous transfer
Figure 15.14 Data Format in Synchronous Communication
In synchronous serial communication, data on the transmission line is output from one falling edge
of the serial clock to the next. Data is guaranteed valid at the rising edge of the serial clock.
In synchronous serial communication, one character consists of data output starting with the LSB
and ending with the MSB. After the MSB is output, the transmission line holds the MSB state.
In synchronous mode, the SCI receives data in synchronization with the rising edge of the serial
clock.
458