R8C datasheet(104/199 Pages) RENESAS

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R8C/10 Group

13.1 Clock Synchronous Serial I/O Mode

Rev.1.20 Jan 27, 2006

page 94 of 180

REJ09B0019-0120

13.1 Clock Synchronous Serial I/O Mode

The clock synchronous serial I/O mode uses a transfer clock to transmit and receive data. This mode can

be selected with UART0. Table 13.1 lists the specifications of the clock synchronous serial I/O mode.

Table 13.2 lists the registers used in clock synchronous serial I/O mode and the register values set.

Item

Specification

Transfer data format

• Transfer data length: 8 bits

Transfer clock

• CKDIR bit in U0MR register is set to “0” (internal clock): fi/(2(n+1))

fi=f1SIO, f8SIO, f32SIO

n=setting value in UiBRG register: 0016 to FF16

• CKDIR bit is set to “1” (external clock ): input from CLK0 pin

Transmission start condition

• Before transmission can start, the following requirements must be met(1)

_ TE bit in U0C1 register is set to “1” (transmission enabled)

_ TI bit in U0C1 register is set to “0” (data present in U0TB register)

Reception start condition

• Before reception can start, the following requirements must be met(1)

_ RE bit in U0C1 register is set to “1” (reception enabled)

_ TE bit in U0C1 register is set to “1” (transmission enabled)

_ TI bit in U0C1 register is set to “0” (data present in the U0TB register)

• For transmission, one of the following conditions can be selected

_ U0IRS bit is set to “0” (transmit buffer empty): when transferring data from

U0TB register to UART0 transmit register (at start of transmission)

_ U0IRS bit is set to “1” (transfer completed): when serial interface finished sending

data from UARTi transmit register

• For reception

When transferring data from the UART0 receive register to the U0RB register (at

completion of reception)

Error detection

• Overrun error(2)

This error occurs if serial interface started receiving the next data before reading the

U0RB register and received the 7th bit of the next data

Select function

• CLK polarity selection

Transfer data I/O can be chosen to occur synchronously with the rising or

the falling edge of the transfer clock

• LSB first, MSB first selection

Whether to start sending/receiving data beginning with bit 0 or beginning with bit 7

can be selected

• Continuous receive mode selection

Reception is enabled immediately by reading the U0RB register

NOTES:

1. When an external clock is selected, the conditions must be met while if the U0C0 register 0 CKPOL bit

= 0 (transmit data output at the falling edge and the receive data taken in at the rising edge of the

transfer clock), the external clock is in the high state; if the CKPOL bit in the U0C0 register is set to “1”

(transmit data output at the rising edge and the receive data taken in at the falling edge of the transfer

clock), the external clock is in the low state.

2. If an overrun error occurs, the value of U0RB register will be indeterminate. The IR bit of S0RIC register

does not change.

Interrupt request

generation timing

Table 13.1 Clock Synchronous Serial I/O Mode Specifications

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