Electrical characteristics
STM32F103xC, STM32F103xD, STM32F103xE
2
Figure 48. I C bus AC waveforms and measurement circuit
V
DD
V
DD
STM32F103xx
SDA
4.7k
4.7k
100
100
I2C bus
SCL
START REPEATED
START
START
t
su(STA)
SDA
t
t
t
r(SDA)
f(SDA)
su(SDA)
t
w(STO:STA)
STOP
t
t
t
w(SCLL)
h(SDA)
h(STA)
SCL
t
t
t
su(STO)
r(SCL)
t
f(SCL)
w(SCLH)
1.
ai14149c
Measurement points are done at CMOS levels: 0.3VDD and 0.7VDD
.
(1)(2)
Table 52. SCL frequency (f
= 36 MHz.,VDD = 3.3 V)
PCLK1
I2C_CCR value
fSCL (kHz)
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.
94/130
Doc ID 14611 Rev 8
STMICROELECTRONICS [ ST ]
