SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
11.3 SIOB DATA BUFFER
0B2H
Bit 7
SIOB7
R/W
0
Bit 6
SIOB6
R/W
0
Bit 5
SIOB5
R/W
0
Bit 4
SIOB4
R/W
0
Bit 3
SIOB3
R/W
0
Bit 2
SIOB2
R/W
0
Bit 1
SIOB1
R/W
0
Bit 0
SIOB0
R/W
0
SIOB
Read/Write
After reset
SIOB is the SIO data buffer register. It stores serial I/O transmit and receive data.
11.4 SIOR REGISTER DESCRIPTION
0B1H
SIOR
Read/Write
After reset
Bit 7
SIOR7
W
Bit 6
SIOR6
W
Bit 5
SIOR5
W
Bit 4
SIOR4
W
Bit 3
SIOR3
W
Bit 2
SIOR2
W
Bit 1
SIOR1
W
Bit 0
SIOR0
W
0
0
0
0
0
0
0
0
The SIOR is designed for the SIO counter to reload the counted value when end of counting. It is like a post-scaler of
SIO clock source and let SIO has more flexible to setting SCK range. Users can set the SIOR value to setup SIO
transfer time. To setup SIOR value equation to desire transfer time is as following.
SCK frequency = SIO rate / (256 - SIOR);
SIOR = 256 - ( 1 / ( SCK frequency ) * SIO rate )
Example: Setup the SIO clock to be 2MHz. Fosc = 12MHz. SIO’s rate = Fcpu/2. Fcpu = Fosc/1 = 12MHz.
SIOR = 256 – (1/(2MHz) * 12MHz/2)
= 256 – 3
= 253
= 0xFD
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