7480 datasheet(143/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

1-126

1.14 Serial I/O

HARDWARE

1.14.3 Clock Asynchronous Serial I/O (UART)

In clock asynchronous serial I/O (UART), the transmit operation of the transmitter and the receive operation

of the receiver are performed simultaneously, synchronizing with the synchronous clock used for transferring,

which is generated by the clock control circuit.

In UART, the transmitter and the receiver have the same transmit/receive baud rate and the same data

transfer format.

UART is selected by clearing the serial I/O mode selection bit of the serial I/O control register to ‘0’.

Data Communication

• Half-duplex communication: one of the two communicating microcomputers operates only as a transmitter

and the other only as a receiver at a time or vice versa.

• Full-duplex communication: both of the two communicating microcomputers operate simultaneously as

transmitter and receiver.

Synchronous Clock

A synchronous clock is selected by the serial I/O synchronous clock selection bit of the serial I/O control

• 0: BRG output /16

• 1: External clock/16 input to the SCLK pin

For the BRG output, refer to (5) Baud Rate Generator in Section 1.14.1.

Notes 1: In UART, the P16/SCLK pin can be used as port pin P16 when the BRG output/16 is selected as

the synchronous clock, since the SCLK pin is not used to output the synchronous clock to the

external.

2: When the external clock/16 is selected as a synchronous clock, keep the HIGH- and the LOW-

width (TWH and TWL) of the pulses used as the external clock source TWH, TWL [s]

≥ (2/f(XIN)

[Hz]). For example, use a frequency of 2 MHz or less (50% duty cycle) as the external clock

source when f(XIN) = 8 MHz.

7480 Datasheet(PDF) 143 Page - Renesas Technology Corp