M37544G Mitsubishi Electric, M37544G Datasheet - Page 25

• Manufacturer Part Number: M37544G
• Description: Single-Chip 8-Bit CMOS Microcomputer
• Manufacturer: Mitsubishi Electric

Serial I/O
Serial I/O can be used as either clock synchronous or asynchro-
nous (UART) serial I/O. A dedicated timer is also provided for
baud rate generation.
Fig. 26 Block diagram of clock synchronous serial I/O
Fig. 27 Operation of clock synchronous serial I/O function
Serial I/O
Write pulse to receive/transmit
buffer register (address 0018
Transfer shift clock
(1/2 to 1/2048 of the internal
clock, or an external clock)
Receive enable signal S
P1
P1
X
P1
P1
IN
Notes 1: As the transmit interrupt (TI), which can be selected, either when the transmit buffer has emptied (TBE=1) or after
0
2
3
1
/S
/R
/S
/T
CLK
RDY
X
X
D
D
2: If data is written to the transmit buffer register when TSC=0, the transmit clock is generated continuously and serial
3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes “1” .
Serial output TxD
Serial input RxD
the transmit shift operation has ended (TSC=1), by setting the transmit interrupt source selection bit (TIC) of the
serial I/O1 control register.
data is output continuously from the TxD pin.
BRG count source selection bit
F/F
RDY
16
)
TBE = 0
1/4
Falling-edge detector
TBE = 1
TSC = 0
Receive buffer register
Receive shift register
D
D
0
0
Transmit buffer register
Transmit shift register
Data bus
Data bus
D
D
Address 0018
Shift clock
Serial I/O synchronous
clock selection bit
Frequency division ratio 1/(n+1)
1
1
Baud rate generator
Address 0018
Shift clock
Address 001C
D
D
2
2
16
(1) Clock Synchronous Serial I/O Mode
Clock synchronous serial I/O mode can be selected by setting the
serial I/O mode selection bit of the serial I/O control register (bit 6)
to “1”.
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.
Clock control circuit
16
Clock control circuit
16
D
D
Serial I/O control register
3
3
Transmit interrupt source selection bit
Receive buffer full flag (RBF)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
Serial I/O status register
1/4
D
D
4
4
MITSUBISHI MICROCOMPUTERS
Receive interrupt request (RI)
D
D
Transmit buffer empty flag (TBE)
Transmit shift completion flag (TSC)
5
5
Transmit interrupt request (TI)
Address 001A
D
D
Address 0019
6
6
7544 Group
Overrun error (OE)
detection
RBF = 1
TSC = 1
D
D
7
7
16
16
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