Polarity Select Function; Lsb First/Msb First Select Function - Renesas R8C/18 Series Hardware Manual

R8C/18 Group, R8C/19 Group
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.
• 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)
CLK0
TXD0
RXD0
• When the CKPOL bit in the U0C0 register = 1 (output transmit data at the rising
edge and input receive data at the falling edge of the transfer clock)
CLK0
TXD0
RXD0
NOTES:
1. When not transferring, the CLK0 pin level is "H".
2. When not transferring, the CLK0 pin level is "L".
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.
• When UFORM bit in U0C0 register = 0 (LSB first)
CLK0
TXD0
RXD0
• When UFORM bit in U0C0 register = 1 (MSB first)
CLK0
TXD0
RXD0
NOTE:
1. The above applies when the CKPOL bit in the U0C0 register is
Figure 15.9 Transfer Format
Rev.1.30 Apr 14, 2006
REJ09B0222-0130
(1)
D0 D1
D0 D1
(2)
D0 D1
D0 D1
D0 D1 D2
D0 D1 D2
D7 D6 D5
D7 D6 D5
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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D2 D3 D4 D5
D2 D3 D4 D5
D2 D3 D4 D5
D2 D3 D4 D5
(1)
D3 D4 D5
D3 D4 D5
(1)
D4 D3 D2
D4 D3 D2
15. Serial Interface
D6 D7
D6 D7
D6 D7
D6 D7
D6 D7
D6 D7
D1 D0
D1 D0