288
User’s Manual U12697EJ3V0UM
CHAPTER 17 3-WIRE SERIAL I/O MODE
Figure 17-1. Block Diagram of Clocked Serial Interface (in 3-Wire Serial I/O Mode)
Internal bus
8
Selector
Serial clock
counter
Interrupt
generator
Serial clock
controller
Serial I/O shift
register 0 (SIO0)
SI0
SO0
SCK0
INTCSI0
TO2
f
XX
/8
f
XX
/16
• Serial I/O shift register 0 (SIO0)
This 8-bit shift register performs parallel to serial conversion and serially communication (shift operation)
synchronized to the serial clock.
SIO0 is set by an 8-bit memory manipulation instruction.
When bit 7 (CSIE0) in serial operation mode register 0 (CSIM0) is one, serial operation starts by writing data to
or reading it from SIO0.
When transmitting, the data written to SIO0 is output to the serial output (SO0).
When receiving, data is read from the serial input (SI0) to SIO0.
RESET input sets SIO0 to 00H.
Caution Do not access SIO0 during a transfer except for an access that becomes a transfer start trigger.
(When MODE0 = 0, reading is disabled; and when MODE0 = 1, writing is disabled.)
