SH7046 Datasheet, PDF (401/611 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7046 Series

Section 12 Serial Communication Interface (SCI)
12.6 Operation in Clocked Synchronous Mode
Figure 12.14 shows the general format for clocked synchronous communication. In clocked
synchronous mode, data is transmitted or received in synchronization with clock pulses. Data is
transferred in 8-bit units. 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 SCI receives data in synchronization 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 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.
*
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 12.14 Data Format in Clocked Synchronous Communication (For LSB-First)
12.6.1 Clock
Either an internal clock generated by the on-chip baud rate generator or an external
synchronization clock input at the SCK pin can be selected, according to the setting of CKE1 and
CKE0 bits in SCR. When the SCI is operated on an internal clock, the serial clock is output from
the SCK pin. Eight serial clock pulses are output in the transfer of one character, and when no
transfer is performed, the clock is fixed high. Only in reception, the serial clock is continued
generating until an overrun error is occurred or the RE bit is cleared to 0. To execute reception in
one-character units, select an external clock as a clock source.
12.6.2 SCI initialization (Clocked Synchronous mode)
Before transmitting and receiving data, you should first clear the TE and RE bits in SCR to 0, then
initialize the SCI as described in a sample flowchart in figure 12.15. When the operating mode,
transfer format, etc., is changed, the TE and RE bits must be cleared to 0 before making the
change using the following procedure. When the TE bit is cleared to 0, the TDRE flag is set to 1.
Rev. 4.00 Dec 05, 2005 page 357 of 564
REJ09B0270-0400