3069RF-ZTAT Datasheet, PDF (522/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

Figure 13.14 shows the general format in synchronous serial communication.
*
Serial clock
One unit (character or frame) of transfer data
*
Serial data
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 transmitting or receiving
Figure 13.14 Data Format in Synchronous Communication
In synchronous serial communication, each data bit is placed on the communication line from one
falling edge of the serial clock to the next. Data is guaranteed valid at the rise of the serial clock.
In each character, the serial data bits are transferred in order from LSB (first) to MSB (last). After
output of the MSB, the communication line remains in the state of the MSB. In synchronous
mode the SCI receives data by synchronizing with the rise of the serial clock.
Communication Format: The data length is fixed at 8 bits. No parity bit or multiprocessor bit
can be added.
Clock: An internal clock generated by the on-chip baud rate generator or an external clock input
from the SCK pin can be selected by means of the C/A bit in SMR and the CKE1 and CKE0 bits
in SCR. See table 13.6 for details of SCI clock source selection.
When the SCI operates on an internal clock, it outputs the clock source at the SCK pin. Eight
clock pulses are output per transmitted or received character. When the SCI is not transmitting or
receiving, the clock signal remains in the high state. If receiving in single-character units is
required, an external clock should be selected.
Transmitting and Receiving Data:
• SCI Initialization (Synchronous Mode): Before transmitting or receiving data, clear the TE and
RE bits to 0 in SCR, then initialize the SCI as follows.
When changing the communication mode or format, always clear the TE and RE bits to 0
before following the procedure given below. Clearing TE to 0 sets the TDRE flag to 1 and
initializes TSR. Note that clearing RE to 0, however, does not initialize the RDRF, PER, and
ORE flags, or RDR, which retain their previous contents.
Rev. 5.0, 09/04, page 500 of 978