MC80F0304/08/16
November 4, 2011 Ver 2.12
81
15. SERIAL INPUT/OUTPUT (SIO)
The serial Input/Output is used to transmit/receive 8-bit data se-
rially. The Serial Input/Output (SIO) module is a serial interface
useful for communicating with other peripheral of microcontrol-
ler devices. These peripheral devices may be serial EEPROMs,
shift registers, display drivers, A/D converters, etc. This SIO is 8-
bit clock synchronous type and consists of serial I/O data register,
serial I/O mode register, clock selection circuit, octal counter and
control circuit as illustrated in Figure 15-1 . The SO pin is de-
signed to input and output. So the Serial I/O(SIO) can be operated
with minimum two pin. Pin R00/SCK, R01/SI, and R02/SO pins
are controlled by the Serial Mode Register. The contents of the
Serial I/O data register can be written into or read out by software.
The data in the Serial Data Register can be shifted synchronously
with the transfer clock signal.
Figure 15-1 SIO Block Diagram
÷
4
÷
16
X
IN
PIN
Pr
es
ca
ler
MUX
SCK[1:0]
00
01
10
11
SCK PIN
SIO
Shift
Input shift register
SIOR
Clock
Clock
Octal
Serial communication
Interrupt
SIOIF
Internal Bus
Counter
SCK[1:0]
“11”
overflow
not “11”
Timer0
Overflow
SI PIN
IOSW
SO PIN
SOUT
IOSW
CONTROL
CIRCUIT
“0”
“1”
POL
1
0
Start
SIOST
clear
SM0
(3-bit)
SIOSF
Complete
