R8CSLASH20 datasheet(290/501 Pages) RENESAS

290 / 501 page

R8C/20 Group, R8C/21 Group

15. Serial Interface

Rev.2.00 Aug 27, 2008

Page 274 of 458

REJ09B0250-0200

15.1.1

Polarity Select Function

Figure 15.8 shows the Transfer Clock Polarity. Use the CKPOL bit in the U0C0 register to select the transfer

clock polarity.

Figure 15.8

Transfer Clock Polarity

15.1.2

LSB First/MSB First Select Function

Figure 15.9 shows the Transfer Format. Use the UFORM bit in the U0C0 register to select the transfer format.

Figure 15.9

Transfer Format

CLK0(1)

TXD0

• When the CKPOL Bit in the U0C0 Register = 0 (output transmit data at the falling

edge and input the receive data at the rising edge of the transfer clock)

NOTES:

1. When not transferring, the CLK0 pin level is “H”.

2. When not transferring, the CLK0 pin level is “L”.

RXD0

CLK0(2)

TXD0

RXD0

• When the CKPOL Bit in the U0C0 Register = 1 (output transmit data at the rising

edge and input the receive data at the falling edge of the transfer clock)

CLK0

TXD0

• When UFORM Bit in U0C0 Register = 0 (LSB first)(1)

RXD0

CLK0

TXD0

RXD0

• When UFORM Bit in U0C0 Register = 1 (MSB first)(1)

NOTE:

1. The above applies when the CKPOL bit in the U0C0 register is set to 0

(output transmit data at the falling edge and input receive data at the

rising edge of the transfer clock).

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