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CHAPTER 16 SERIAL INTERFACE (SIO31)
Preliminary User’s Manual U13420EJ2V0UM00
Notes 1. When CSIE31 = 0 (SIO31 operation stop status), the pins SI31, SO31, and SCK31 can be used for
port functions.
2. When CSIE31 = 1 (SIO31 operation enabled state), the SI31 pin can be used as a port pin if only the
send function is used, and the SO31 pin can be used as a port pin if only the receive-only mode is
used.
Remarks 1. f
X
: main system clock oscillation frequency
2. Figures in parentheses are for operation with f
X
= 8.38 MHz.
(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
in synchronization with the serial clock.
The serial I/O shift register 31 (SIO31) is shifted in synchronization with the falling edge of the serial clock.
Transmission data is held in the SO31 latch and is output from the SO31 pin. Data that is received via the SI31
pin in synchronization with the rising edge of the serial clock is latched to SIO31.
Completion of an 8-bit transfer automatically stops operation of SIO31 and sets interrupt request flag (CSIIF31).
Figure 16-3. Timing of 3-Wire Serial I/O Mode
(3) Transfer start
A serial transfer starts when the following two conditions have been satisfied and transfer data has been set (or
read) to serial I/O shift register 31 (SIO31).
• The SIO31 operation control bit (CSIE31) = 1
• After an 8-bit serial transfer, either the internal serial clock is stopped or SCK31 is set to high level.
• Transmit/transmit and receive mode
When CSIE31 = 1 and MODE1 = 0, transfer starts when writing to SIO31.
• Receive-only mode
When CSIE31 = 1 and MODE1 = 1, transfer starts when reading from SIO31.
Caution
After data has been written to SIO31, transfer will not start even if the CSIE31 bit value is set
to “1”.
Completion of an 8-bit transfer automatically stops the serial transfer operation and interrupt request flag
(CSIIF31) is set.
SI31
DI7
DI6
DI5
DI4
DI3
DI2
DI1
DI0
CSIIF31
SCK31
1
SO31
DO7
DO6
DO5
DO4
DO3
DO2
DO1
DO0
2
3
4
5
6
7
8
Transfer completion
Transfer starts in synchronization with the SCK31 falling edge
Содержание mPD780065 Series
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