SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
7542 Group
MITSUBISHI MICROCOMPUTERS
47
PRELIMINAR
Y
Notice:
This
is not
a final
specification.
Some
parametric
limits
are
subject
to change.
Fig. 58 Block diagram of clock synchronous serial I/O2
Fig. 59 Operation of clock synchronous serial I/O2 function
qSerial I/O2
Serial I/O2 can be used as either clock synchronous or asynchro-
nous (UART) serial I/O. A dedicated timer is also provided for
baud rate generation.
(1) Clock Synchronous Serial I/O Mode
Clock synchronous serial I/O2 mode can be selected by setting
the serial I/O2 mode selection bit of the serial I/O2 control register
(bit 6) to “1”.
For clock synchronous serial I/O2, 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.
D7
D0
D1
D2
D3
D4
D5
D6
D0
D1
D2
D3
D4
D5
D6
RBF = 1
TSC = 1
TBE = 0
TBE = 1
TSC = 0
Transfer shift clock
(1/2 to 1/2048 of the internal
clock, or an external clock)
Serial output TxD2
Serial input RxD2
Write pulse to receive/transmit
buffer register (address 002E16)
Overrun error (OE)
detection
Notes 1: As the transmit interrupt (TI), which can be selected, 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/O2 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” .
Receive enable signal SRDY2
1/4
F/F
P06/SCLK2
Serial I/O2 status register
Serial I/O2 control register
P07/SRDY2
P04/RXD2
P05/TXD2
XIN
Receive buffer register 2
Address 002E16
Receive shift register 2
Receive buffer full flag (RBF)
Receive interrupt request (RI)
Clock control circuit
Shift clock
Serial I/O2 synchronous
clock selection bit
Frequency division ratio 1/(n+1)
Baud rate generator 2
Address 003216
BRG count source selection bit
Clock control circuit
Falling-edge detector
Transmit buffer register 2
Data bus
Address 002E16
Shift clock
Transmit shift completion flag (TSC)
Transmit buffer empty flag (TBE)
Transmit interrupt request (TI)
Transmit interrupt source selection bit
Address 002F16
Data bus
Address 003016
Transmit shift register 2