
24
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
38C3 Group
Data bus
XCIN
XIN
Serial I/O
interrupt request
P4
6 latch
P4
5 latch
Serial I/O port selection bit
P47 latch
Serial I/O counter (3)
Serial I/O shift register (8)
Synchronous
circuit
Internal
system clock
selection bit
Serial I/O port selection bit
“1”
“0”
SCLK
SRDY output selection bit
External clock
Synchronous clock
selection bit
Divider
1/8
1/16
1/32
1/64
1/128
1/256
Internal synchronous
clock selection bits
P46/SCLK1
P45/SOUT
P44/SIN
SRDY
P47/SRDY
P40 latch
Serial I/O port selection bit
P40/SCLK2
“1”
“0”
“1”
“0”
“1”
“0”
“1”
“0”
“1”
“0”
SERIAL I/O
The 38C3 group has a built-in 8-bit clock synchronous serial I/O. The
I/O pins of serial I/O also operate as I/O port P4, and their function is
selected by the serial I/O control register 1 (address 001916).
Fig. 22 Block diagram of serial I/O
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