
R8C/2C Group, R8C/2D Group
15. Serial Interface
Rev.2.00
Dec 05, 2007
REJ09B0339-0200
15.1
Clock Synchronous Serial I/O Mode
In clock synchronous serial I/O mode, data is transmitted and received using a transfer clock.
i = 0 to 2
NOTES:
1. If an external clock is selected, ensure that the external clock is “H” when the CKPOL bit in the UiC0
register is set to 0 (transmit data output at falling edge and receive data input at rising edge of
transfer clock), and that the external clock is “L” when the CKPOL bit is set to 1 (transmit data output
at rising edge and receive data input at falling edge of transfer clock).
2. If an overrun error occurs, the receive data (b0 to b8) of the UiRB register will be undefined. The IR
bit in the SiRIC register remains unchanged.
Table 15.1
Clock Synchronous Serial I/O Mode Specifications
Item
Specification
Transfer data format
Transfer data length: 8 bits
Transfer clocks
CKDIR bit in UiMR register is set to 0 (internal clock): fi/(2(n+1))
fi = f1, f8, f32 n = value set in UiBRG register: 00h to FFh
The CKDIR bit is set to 1 (external clock): input from CLKi pin
Transmit start conditions
Before transmission starts, the following requirements must be me
t(1)- The TE bit in the UiC1 register is set to 1 (transmission enabled)
- The TI bit in the UiC1 register is set to 0 (data in the UiTB register)
Receive start conditions
Before reception starts, the following requirements must be me
t(1)- The RE bit in the UiC1 register is set to 1 (reception enabled)
- The TE bit in the UiC1 register is set to 1 (transmission enabled)
- The TI bit in the UiC1 register is set to 0 (data in the UiTB register)
Interrupt request
generation timing
When transmitting, one of the following conditions can be selected
- The UiIRS bit is set to 0 (transmit buffer empty):
When transferring data from the UiTB register to UARTi transmit register
(when transmission starts).
- The UiIRS bit is set to 1 (transmission completes):
When completing data transmission from UARTi transmit register.
When receiving
When data transfer from the UARTi receive register to the UiRB register
(when reception completes).
Error detection
This error occurs if the serial interface starts receiving the next data item
before reading the UiRB register and receives the 7th bit of the next data.
Select functions
CLK polarity selection
Transfer data input/output can be selected to occur synchronously with the
rising or the falling edge of the transfer clock.
LSB first, MSB first selection
Whether transmitting or receiving data begins with bit 0 or begins with bit 7
can be selected.
Continuous receive mode selection
Receive is enabled immediately by reading the UiRB register.