CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
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Figure 11-5. Block Diagram of 3-Wire Serial I/O (CSI4)
Baud rate
generator
SO4
SI4
INTCSI4
Serial clock controller
Selector
Interrupt
generator
Serial clock counter
(8-/16-bit switchable)
Variable-length serial I/O
shift register 4 (8 to 16 bits)
SCK4
Direction controller
Internal bus
(1) Variable-length serial I/O shift register 4 (SIO4)
SIO4 is a 16-bit variable register that performs parallel-serial conversion and transmission/reception (shift
operations) in synchronization with the serial clock.
SIO4 is set by a 16-bit memory manipulation instruction.
When bit 7 (CSIE4) of variable-length serial control register 4 (CSIM4) is set to 1, a serial operation can be
started by writing data to or reading data from SIO4.
When transmitting, data written to SIO4 is output via the serial output (SO4).
When receiving, data is read from the serial input (SI4) and written to SIO4.
RESET input sets SIO4 to 0000H.
Caution
Do not access SIO4 except by the transfer start trigger during a transfer operation (read is
disabled when MODE4 = 0 and write is disabled when MODE4 = 1).
After reset: 0000H R/W
Address: FFFFF2E0H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
SIO4