SH7708 Datasheet, PDF (372/625 Pages) Renesas Technology Corp – SuperH™ RISC engine

1 3 . 3 Operation
13.3.1 Overview
For serial communication, the SCI has an asynchronous mode in which characters are synchronized
individually, and a synchronous mode in which communication is synchronized with clock pulses.
Asynchronous/synchronous mode and the transmission format are selected in the serial mode
register (SCSMR), as shown in table 13.9. The SCI clock source is selected by the combination
of the C/A bit in the serial mode register (SCSMR) and the CKE1 and CKE0 bits in the serial
control register (SCSCR), as shown in table 13.10.
Asynchronous Mode:
• Data length is selectable: seven or eight bits.
• Parity and multiprocessor bits are selectable, as is the stop bit length (one or two bits). The
combination of the preceding selections constitutes the communication format and character
length.
• In receiving, it is possible to detect framing errors (FER), parity errors (PER), overrun errors
(ORER) and breaks.
• An internal or external clock can be selected as the SCI clock source.
 When an internal clock is selected, the SCI operates using the on-chip baud rate generator,
and can output a serial clock signal with a frequency matching the bit rate.
 When an external clock is selected, the external clock input must have a frequency 16 times
the bit rate. (The on-chip baud rate generator is not used.)
Synchronous Mode:
• The transmission/reception format has a fixed eight-bit data length.
• In receiving, it is possible to detect overrun errors (ORER).
• An internal or external clock can be selected as the SCI clock source.
 When an internal clock is selected, the SCI operates using the on-chip baud rate generator,
and outputs a serial clock to external devices.
 When an external clock is selected, the SCI operates on the input serial clock. The on-chip
baud rate generator is not used.
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