Operation In Clocked Synchronous Mode; Clock; Figure 14.9 Data Format In Clocked Synchronous Communication - Renesas H8 Series Hardware Manual

14.5

Operation in Clocked Synchronous Mode

Figure 14.9 shows the general format for clocked synchronous communication. In clocked
synchronous mode, data is transmitted or received synchronous with clock pulses. A single
character in the transmit data consists of the 8-bit data starting from the LSB. In clocked
synchronous serial communication, data on the transmission line is output from one falling edge of
the serial clock to the next. In clocked synchronous mode, the SCI3 receives data in synchronous
with the rising edge of the serial clock. After 8-bit data is output, the transmission line holds the
MSB state. In clocked synchronous mode, no parity or multiprocessor bit is added. Inside the
SCI3, the transmitter and receiver are independent units, enabling full-duplex communication
through the use of a common clock. Both the transmitter and the receiver also have a double-
buffered structure, so data can be read or written during transmission or reception, enabling
continuous data transfer.
Synchronization

clock

Serial data
Note: * High except in continuous transfer

Figure 14.9 Data Format in Clocked Synchronous Communication

14.5.1 Clock
Either an internal clock generated by the on-chip baud rate generator or an external
synchronization clock input at the SCK3 pin can be selected, according to the setting of the COM
bit in SMR and CKE0 and CKE1 bits in SCR3. When the SCI3 is operated on an internal clock,
the serial clock is output from the SCK3 pin. Eight serial clock pulses are output in the transfer of
one character, and when no transfer is performed the clock is fixed high.
One unit of transfer data (character or frame)
*
LSB
Bit 0 Bit 1
Don't care
Section 14 Serial Communication Interface 3 (SCI3)
8-bit
Bit 2 Bit 3 Bit 4 Bit 5
Rev. 1.00 Aug. 28, 2006 Page 223 of 400
*
MSB
Bit 6 Bit 7
Don't care
REJ09B0268-0100