HD64F3694HV Datasheet, PDF (243/452 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Tiny Series

Section 14 Serial Communication Interface 3 (SCI3)
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.
8-bit
*
Synchronization
clock
Serial data
One unit of transfer data (character or frame)
*
LSB
MSB
Bit 0 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit 6 Bit 7
Don’t care
Don’t care
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.
14.5.2 SCI3 Initialization
Before transmitting and receiving data, the SCI3 should be initialized as described in a sample
flowchart in figure 14.4.
Rev.5.00 Nov. 02, 2005 Page 213 of 418
REJ09B0028-0500