REJ03B0166-0113 Rev.1.13
Aug 21, 2009
3803 Group (Spec.H QzROM version)
(2) Asynchronous Serial I/O (UART) Mode
Clock asynchronous serial I/O mode (UART) can be selected by
clearing the serial I/O1 mode selection bit (b6) of the serial I/O1
control register to “0”.
Eight serial data transfer formats can be selected, and the transfer
formats used by a transmitter and receiver must be identical.
The transmit and receive shift registers each have the buffer
register 1, but the two buffer registers have the same address in a
memory. Since the shift register cannot be written to or read from
directly, transmit data is written to the transmit buffer register 1,
and receive data is read from the receive buffer register 1.
The transmit buffer register 1 can also hold the next data to be
transmitted, and the receive buffer register 1 can hold a character
while the next character is being received.
Fig 38. Block diagram of UART serial I/O1
Fig 39. Operation of UART serial I/O1
f(XIN)
1/4
OE
PE FE
1/16
Data bus
Receive buffer register 1
Address 001816
Receive shift register 1
Receive buffer full flag (RBF)
Receive interrupt request (RI)
Baud rate generator
Frequency division ratio 1/(n+1)
Address 001C16
ST/SP/PA generator
Transmit buffer register 1
Transmit shift register 1
Address 001816
Transmit shift
completion flag (TSC)
Transmit buffer empty flag (TBE)
Transmit interrupt request (TI)
Address 001916
ST detector
SP detector
UART1 control register
Address 001B16
Character length selection bit
Address 001A16
BRG count source selection bit
Transmit interrupt source selection bit
Serial I/O1 synchronous clock selection bit
Clock control circuit
Character length selection bit
7 bits
8 bits
Serial I/O1 status register
Serial I/O1 control register
P46/SCLK1
P44/RXD1
P45/TXD1
(f(XCIN) in low-speed mode)
TSC=0
TBE=1
RBF=0
TBE=0
RBF=1
TBE=1
TSC=1*
ST
D0
D1
SP
D0
D1
ST
SP
Transmit or
receive clock
Transmit buffer register 1
write signal
Serial output
TXD1
Receive buffer register 1
read signal
Serial input RXD1
Generated at 2nd bit in 2-stop-bit mode
1 start bit
7 or 8 data bit
1 or 0 parity bit
1 or 2 stop bit (s)
Notes 1: Error flag detection occurs at the same time that the RBF flag becomes “1” (at 1st stop bit, during reception).
2: As the transmit interrupt (TI), when either the TBE or TSC flag becomes “1”, can be selected to occur depending on the setting of the transmit interrupt source
selection bit (TIC) of the serial I/O1 control register.
3: The receive interrupt (RI) is set when the RBF flag becomes “1”.
4: After data is written to the transmit buffer when TSC=1, 0.5 to 1.5 cycles of the data shift cycle are necessary until changing to TSC=0.
ST
D0
D1
SP
D0
D1
ST
SP