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CHAPTER 14 SERIAL INTERFACE SIO2
Preliminary User’s Manual U14581EJ3V0UM00
(c) Transfer format when CLPH = 1
Figure 14-7 shows the operation timing when CLPH = 1. Two waves of SCK2, when CLPO = 1 and when
CLPO = 0, are shown in the figure.
Data is transmitted or received in 8-bit units. Each bit of data is transmitted or received in synchronization
with the serial clock.
SIO2 is shifted at the falling edge of SCK2 if CLPH = 1 and CLPO = 0. If CLPH = 1 and CLPO = 1, SIO2
is shifted at the rising edge of SCK2. The transmit data is held by the SO2 latch and output from the SO2
pin. The receive data input to the SI2 pin is latched to SIO2 at the falling edge of SCK2 (if CLPH = 1 and
CLOP = 0).
Completion of an 8-bit transfer automatically stops operation of SIO2 and sets a serial transfer completion
flag.
Figure 14-7. Operation Timing When CLPH Is Set to 1
(Serial output data: 55H, serial input data: AAH)
ABH
56H
ADH
5AH
B5H
6AH
D5H
AAH
AAH
(AAH)
(55H)
SCK2
(CLPO = 0)
SIRB2
SI2
SO2
SCK2
(CLPO = 1)
55H
(Write: SIO2 = 55H)
Serial output
data timing
Start trigger
operation timing
INTCSI2
(interrupt request
generated at rising edge)
(6) Hardware detection in error status
Serial interface SIO2 has a function for checking whether an overflow error has occurred.
While serial data being transferred to the serial receive data buffer register (SIRB2) has not yet been read, the
overflow flag (SDOF) is set to 1 if the capture strobe of the LSB of the serial data to be transferred next has
occurred.
If an overflow has occurred, the received serial data is not transferred to SIRB2. Therefore, data that has already
been received and transferred to SIRB2 can be read. In this way, the loss of receive data is prevented even
if an overflow error occurs.
SDOF is cleared by reading the serial receive data buffer status register (SRBS2).
If SIRB2 is read to monitor the status of serial interface SIO2, always monitor SRBS2 to check whether an interrupt
request (overflow error) has occurred.
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