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98
μ
PD75236
SCK0
SB0/SB1
IRQCSI0
1
2
3
4
5
6
7
8
D7
D6
D5
D4
D3
D2
D1
D0
Execution of data write instruction to SIO0
(Transfer Start Command)
Transfer start at the falling edge of SCK0
End of Transfer
(c)
2-wire serial I/O mode operations
The 2-wire serial I/O mode can be applied to any communication format by program.
Communication is basically carried out using two lines of serial clock (SCK0) and serial data input/
output (SB0 or SB1).
(i)
Communication
The 2-wire serial I/O mode is used for data transmission and reception in 8-bit units. Bit-wise data
transmission/reception is carried out in synchronization with the serial clock.
Shift operation of shift register 0 is carried out at the falling edge of serial clock (SCK0). Transmit
data is held at the SO0 latch and output from the SB0/P02 (or SB1/P03) pin with MSB set as the first
bit. Receive data input from the SB0 (or SB1) pin at the SCK0 rising edge is latched to the shift
register 0.
Upon termination of 8-bit transfer, the shift register 0 operation automatically stops and the
interrupt request flag (IRQCSI0) is set.
Fig. 4-51 2-Wire Serial I/O Mode Timing
Since the pin specified for the serial data bus of the SB0 (or SB1) pin becomes an N-ch open drain
input/output, it must be pulled up externally.
Since the SB0 (or SB1) pin outputs the SO0 latch status, the SB0 (or SB1) pin status can be
manipulated by setting the RELT and CMDT bits.
However, do not carry out this operation during serial transfer.
The SCK0 pin can control the output status by manipulating the P01 output latch in the output
mode (internal system clock mode) (refer to
4.9 (7) SCK0 pin output manipulation
).