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CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
387
(a) I
2
Cn transfer clock setting method
The I
2
Cn transfer clock frequency (f
SCL
) is calculated using the following expression (n = 0, 1).
f
SCL
= 1/(m
×
T + t
R
+ t
F
)
m = 12, 24, 48, 36, 54, 44, 86, 172, 132, 198 (see the descriptions for bits IICCEn1, IICCEn0,
CLXn, SMCn, CLn1, and CLn0 in
11.5.2 (4)
.)
T:
1/f
XX
t
R
:
SCLn rise time
t
F
:
SCLn fall time
For example, the I
2
Cn transfer clock frequency (f
SCL
) when f
XX
= 20 MHz, m = 198, t
R
= 200 ns, and t
F
=
50 ns is calculated using following expression.
f
SCL
= 1/(198
×
50 ns + 200 ns + 50 ns)
≅
98.5 kHz
m
×
T + t
R
+ t
F
m/2
×
T
t
F
t
R
m/2
×
T
SCLn
SCLn inversion
SCLn inversion
SCLn inversion
(5) IIC shift registers 0, 1 (IIC0, IIC1)
IICn is used for serial transmission/reception (shift operations) synchronized with the serial clock. It can be
read from or written to in 8-bit units, but data should not be written to IICn during a data transfer (n = 0, 1).
After reset: 00H
R/W
Address: FFFFF348H, FFFFF358H
7
6
5
4
3
2
1
0
IICn
(n = 0, 1)
(6) Slave address registers 0, 1 (SVA0, SVA1)
SVAn holds the I
2
C bus’s slave addresses.
It can be read from or written to in 8-bit units, but bit 0 should be fixed to 0.
After reset: 00H
R/W
Address: FFFFF346H, FFFFF356H
7
6
5
4
3
2
1
0
SVAn
0
(n = 0, 1)