Technical information

29
MITSUBISHI MICROCOMPUTERS
3820 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
SERIAL I/O2
The serial I/O2 function can be used only for clock synchronous
serial I/O.
For clock synchronous serial I/O2 the transmitter and the receiver
must use the same clock. If the internal clock is used, transfer is
started by a write signal to the serial I/O2 register.
Serial I/O2 Control Register (SIO2CON) 001D16
The serial I/O2 control register contains 7 bits which control vari-
ous serial I/O functions.
Fig. 20 Structure of serial I/O2 control register
Fig. 21 Block diagram of serial I/O2 function
Serial I/O2 control register
(SIO2CON : address 001D
16 )
b7
Internal synchronization clock select bits
0 0 0: f(X IN )/8
0 0 1: f(X
IN )/16
0 1 0: f(X
IN )/32
0 1 1: f(X
IN )/64
1 0 0:
1 0 1:
1 1 0: f(X
IN )/128
1 1 1: f(X
IN )/256
Serial I/O2 port selection bit
0: I/O port
1: S
OUT2 ,S CLK2 signal output
S
RDY2 output enable bit
0: I/O port
1: S
RDY2 signal output
Transfer direction selection bit
0: LSB first
1: MSB first
Synchronization clock selection bit
0: External clock
1: Internal clock
Not used (returns “0” when read)
b0
b2 b1 b0
Do not set
X IN
"1"
"0"
"0"
"1"
"0"
"1"
S RDY2
S
CLK2
"0"
"1"
1/8
1/16
1/32
1/64
1/128
1/256
Data bus
Serial I/O2
interrupt request
Serial I/O2 port selection bit
Serial I/O counter 2 (3)
Serial I/O shift register 2 (8)
Synchronization circuit
Serial I/O2 port selection bit
Synchronization clock
selection bit
S
RDY2 output enable bit
External clock
Internal synchronization
clock select bits
Divider
P5 3 latch
P5 3 /S RDY2
P5 2 /S CLK2
P5 1 /S OUT2
P5 0 /S IN2
P5 2 latch
P5
1 latch