
R8C/14 Group, R8C/15 Group 14. Serial Interface
Rev.2.10 Jan 19, 2006 Page 136 of 253
REJ09B0164-0210
NOTES:
1. The bits used for transmit/receive data are as follows: Bits 0 to 6 when transfer data is 7-bit long; bits
0 to 7 when transfer data is 8-bit long; bits 0 to 8 when transfer data is 9-bit long.
Table 14.6 lists the I/O Pin Functions in Clock Asynchronous Serial I/O Mode. After the UART0 operating
mode is selected, the TXD0 pin outputs “H” level (If the NCH bit is set to “1” (N-channel open-drain
outputs), this pin is in a high-impedance state) until transfer starts.
Table 14.5 Registers to Be Used and Settings in UART Mode
Register Bit Function
U0TB 0 to 8
Set transmit data
(1)
U0RB 0 to 8
Receive data can be read
(1)
OER,FER,PER,SUM Error flag
U0BRG 0 to 7 Set a bit rate
U0MR SMD2 to SMD0 Set to “100b” when transfer data is 7-bit long
Set to “101b” when transfer data is 8-bit long
Set to “110b” when transfer data is 9-bit long
CKDIR Select the internal clock or external clock
STPS Select the stop bit
PRY, PRYE Select whether parity is included and odd or even
U0C0 CLK0, CLK1 Select the count source for the U0BRG register
TXEPT Transmit register empty flag
NCH Select TXD0 pin output mode
CKPOL Set to “0”
UFORM LSB first or MSB first can be selected when transfer data is 8-bit
long. Set to “0” when transfer data is 7- or 9-bit long.
U0C1 TE Set to “1” to enable transmit
TI Transmit buffer empty flag
RE Set to “1” to enable receive
RI Receive complete flag
UCON U0IRS, U1IRS Select the factor of UART0 transmit interrupt
U0RRM Set to “0”
CNTRSEL
Set to “1” to select P1_5/RXD0/CNTR01/INT11
Table 14.6 I/O Pin Functions in Clock Asynchronous Serial I/O Mode
Pin name Function Selection Method
TXD0(P1_4) Output serial data (Cannot be used as a port when performing receive only)
RXD0(P1_5) Input serial data PD1_5 bit in PD1 register=0
(P1_5 can be used as an input port when performing transmit
only)
CLK0(P1_6) Programmable I/O Port CKDIR bit in U0MR register=0
Input transfer clock CKDIR bit in U0MR register=1
PD1_6 bit in PD1 register=0
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