M3850 RENESAS [Renesas Technology Corp], M3850 Datasheet - Page 24

• Manufacturer Part Number: M3850
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
• Manufacturer: RENESAS [Renesas Technology Corp]

3850 Group (Spec.A)
SERIAL INTERFACE
Serial I/O1 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. 20 Block diagram of clock synchronous serial I/O1
Fig. 21 Operation of clock synchronous serial I/O1 function
Rev.2.10
REJ03B0093-0210
SERIAL I/O1
Write pulse to receive/transmit
buffer register (address 0018
Receive enable signal S
Transfer shift clock
(1/2 to 1/2048 of the internal
clock, or an external clock)
Notes 1: As the transmit interrupt (TI), either when the transmit buffer has emptied (TBE=1) or after the transmit shift operation has
P2
P2
2005.11.14
P2
P2
7
6
/S
/S
4
5
/R
2: If data is written to the transmit buffer register when TSC=0, the transmit clock is generated continuously and serial data
3: The receive interrupt (RI) is set when the receive buffer full flag (RBF) becomes “1” .
/T
RDY1
Serial output TxD
CLK1
Serial input RxD
X
X
X
ended (TSC=1), by setting the transmit interrupt source selection bit (TIC) of the serial I/O1 control register.
is output continuously from the TxD pin.
D
IN
D
BRG count source selection bit
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RDY1
F/F
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
1
1
Address 0018
Shift clock
Serial I/O1 synchronous
clock selection bit
Frequency division ratio 1/(n+1)
Baud rate generator
Address 0018
Shift clock
Address 001C
D
D
2
2
(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 001A
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.
16
Clock control circuit
16
Clock control circuit
16
D
D
3
3
Serial I/O1 control register
Transmit interrupt source selection bit
Receive buffer full flag (RBF)
Serial I/O1 status register
1/4
D
D
16
4
4
) to “1”.
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
Overrun error (OE)
detection
RBF = 1
TSC = 1
D
D
16
7
7
16