HD64F2357VF13 Datasheet, PDF (535/1049 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

14.3.4 Operation in Clocked Synchronous Mode
In clocked 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 14-14 shows the general format for clocked 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 14-14 Data Format in Synchronous Communication
In clocked synchronous serial communication, data on the transmission line is output from one falling edge of the serial
clock to the next. Data confirmation is guaranteed at the rising edge of the serial clock.
In clocked 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 clocked synchronous mode, the SCI receives data in synchronization with the rising edge of the serial clock.
Data Transfer Format: A fixed 8-bit data format is used.
No parity or multiprocessor bits are added.
Clock: Either an internal clock generated by the on-chip baud rate generator or an external serial clock input at the SCK
pin can be selected, according to the setting of the C/A bit in SMR and the CKE1 and CKE0 bits in SCR. For details of
SCI clock source selection, see table 14-9.
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. When only receive operations are performed, however, the serial clock is output until an overrun error occurs or the
RE bit is cleared to 0. If you want to perform receive operations in units of one character, you should select an external
clock as the clock source.
Rev.6.00 Oct.28.2004 page 505 of 1016
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