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Chapter 13
Serial Interface SIO30
User’s Manual U16504EE1V1UD00
<When SIO30 is used>
(2)
Communication Operations
In the three-wire serial I/O mode, data is transmitted and received in 8-bit units. Each bit of data is
sent or received synchronized with the serial clock.
The serial I/O shift register (SIO30) is shifted synchronized with the falling edge of the serial clock.
The transmission data is held in the SO30 latch and is transmitted from the SO30 pin. The data is
received via the SI30 pin synchronized with the rising edge of the serial clock is latched to SIO30.
The completion of an 8-bit transfer automatically stops operation of SIO30 and sets a serial trans-
fer completion flag.
Figure 13-5:
Timing of Three-wire Serial I/O Mode
Modes
Values
Settings
During serial clock output
(master transmission or master reception)
PM35 = 0
Sets P35 (SCK30) to output mode
P35 = 0
Sets output latch of P35 to 0
During serial clock input
(slave transmission or slave reception)
PM35 = 1
Sets P35 (SCK30) to input mode
Transmit/receive mode
PM36 = 0
Sets P36 (SO30) to output mode
P36 = 0
Sets output latch of P36 to 0
Receive mode
PM37 = 1
Sets P37 (SI30) to input mode
SI30
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
Serial transfer
completion flag
SCK30
1
SO30
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
2
3
4
5
6
7
8
Transfer completion
Transfer starts in synchronized with the serial clock’s falling edge