3858 Group
SERIAL INTERFACE
(1) Clock Synchronous Serial I/O Mode
Clock synchronous serial I/O mode can be selected by setting the
serial I/O1 mode selection bit of the serial I/O1 control register (bit
6 of address 001A16) to “1”.
■SERIAL I/O1
Serial I/O1 can be used as either clock synchronous or asynchro-
nous (UART) serial I/O1. A dedicated timer is also provided for
baud rate generation.
For clock synchronous serial I/O, the transmitter and the receiver
must use the same clock. If an internal clock is used, transfer is
started by a write signal to the TB/RB.
Data bus
Serial I/O1 control register
Address 001A16
Address 001816
Receive buffer register
Receive buffer full flag (RBF)
Receive shift register
Receive interrupt request (RI)
P24/RXD
Shift clock
Clock control circuit
P26/SCLK1
Serial I/O1 synchronous
clock selection bit
Frequency division ratio 1/(n+1)
BRG count source selection bit
1/4
X
IN
Baud rate generator
Address 001C16
1/4
Clock control circuit
Falling-edge detector
P27/SRDY1
F/F
Shift clock
Transmit shift register
Transmit buffer register
Transmit shift completion flag (TSC)
Transmit interrupt source selection bit
P25/TXD
Transmit interrupt request (TI)
Transmit buffer empty flag (TBE)
Serial I/O1 status register
Address 001916
Address 001816
Data bus
Fig. 36 Block diagram of clock synchronous serial I/O1
Transfer shift clock
(1/2 to 1/2048 of the internal
clock, or an external clock)
Serial output TxD
Serial input RxD
D
0
0
D
1
1
D
2
2
D
3
3
D
4
4
D
5
5
D
6
6
D
7
7
D
D
D
D
D
D
D
D
Receive enable signal SRDY1
Write pulse to receive/transmit
buffer register (address 001816
)
RBF = 1
TSC = 1
Overrun error (OE)
detection
TBE = 0
TBE = 1
TSC = 0
Notes 1: As the transmit interrupt (TI), either when the transmit buffer has emptied (TBE=1) or after the transmit shift operation has
ended (TSC=1), by setting the transmit interrupt source selection bit (TIC) of the serial I/O1 control register.
2: If data is written to the transmit buffer register when TSC=0, the transmit clock is generated continuously and serial data
is output continuously from the TxD pin.
3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes “1” .
Fig. 37 Operation of clock synchronous serial I/O1 function
Rev.1.10 Apr 3, 2006 page 43 of 75
REJ03B0139-0110
RENESAS [ RENESAS TECHNOLOGY CORP ]
