Electrical characteristics
STM32F105xx, STM32F107xx
2
Figure 24. I C bus AC waveforms and measurement circuit
V
V
DD
DD
STM32F10x
SDA
4.7kΩ
4.7kΩ
100 Ω
100 Ω
I²C bus
SCL
Start repeated
Start
Start
t
su(STA)
SDA
t
t
t
su(SDA)
f(SDA)
r(SDA)
t
su(STO:STA)
Stop
t
t
t
h(SDA)
h(STA)
w(SCLL)
SCL
t
t
t
t
f(SCL)
su(STO)
w(SCLH)
r(SCL)
ai14133d
Measurement points are done at CMOS levels: 0.3VDD and 0.7VDD
.
1.
(1)(2)
Table 42. SCL frequency (f
fSCL (kHz)
= 36 MHz.,VDD = 3.3 V)
PCLK1
I2C_CCR value
RP = 4.7 kΩ
400
300
200
100
50
0x801E
0x8028
0x803C
0x00B4
0x0168
0x0384
20
1. RP = External pull-up resistance, fSCL = I2C speed,
2. For speeds around 200 kHz, the tolerance on the achieved speed is of ±5%. For other speed ranges, the
tolerance on the achieved speed ±2%. These variations depend on the accuracy of the external
components used to design the application.
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Doc ID 15274 Rev 6
STMICROELECTRONICS [ ST ]
