CHAPTER 12 SERIAL INTERFACE 20
(2) Communication operation
In 3-wire serial I/O mode, data transmission/reception is performed in 8-bit units.
transmitted/received bit by bit in synchronization with the serial clock.
Data is
Transmission shift register (TXS20/SIO20) and reception shift register (RXS20) shift operations are
performed in synchronization with the fall of the serial clock (SCK20). Then transmit data is held in the
SO20 latch and output from the SO20 pin. Also, receive data input to the SI20 pin is latched in the
reception buffer register (RXB20/SIO20) on the rise of SCK20.
At the end of an 8-bit transfer, the operation of TXS20/SIO20 and RXS20 stops automatically, and the
interrupt request signal (INTCSI20) is generated.
Figure 12-11. 3-Wire Serial I/O Mode Timing (1/7)
(i) Master operation timing (when DAP20 = 0, CKP20 = 0, SSE20 = 0)
SIO20
write
SCK20
SO20
1
2
3
4
5
6
7
8
Note
DO7
DI7
DO6
DI6
DO5
DI5
DO4
DI4
DO3
DI3
DO2
DI2
DO1
DI1
DO0
DI0
SI20
INTCSI20
Note The value of the last bit previously output is output.
User’s Manual U15075EJ1V0UM00
240
NEC [ NEC ]
