R8C/1A Group, R8C/1B Group
15. Serial Interface
Rev.1.30
Dec 08, 2006
Page 161 of 315
REJ09B0252-0130
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)
D0
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)
D1
D2
NOTES :
1. When not transferring, the CLK0 pin level is “H”.
2. When not transferring, the CLK0 pin level is “L”.
D3
D4
D5
D6
D7
D0
RXD0
D1
D2
D3
D4
D5
D6
D7
CLK0
(2)
D0
TXD0
D1
D2
D3
D4
D5
D6
D7
D0
RXD0
D1
D2
D3
D4
D5
D6
D7
• 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
D0
TXD0
• When UFORM bit in U0C0 register = 0 (LSB first)
(1)
D1
D2
D3
D4
D5
D6
D7
D0
RXD0
D1
D2
D3
D4
D5
D6
D7
CLK0
D7
TXD0
D6
D5
D4
D3
D2
D1
D0
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).
D7
D6
D5
D4
D3
D2
D1
D0