STM32F103x8, STM32F103xB
Electrical characteristics
5.3.15
Communications interfaces
I
2
C interface characteristics
Unless otherwise specified, the parameters given in
are derived from tests
performed under the ambient temperature, f
PCLK1
frequency and V
DD
supply voltage
conditions summarized in
The STM32F103xx performance line I
2
C interface meets the requirements of the standard
I
2
C communication protocol with the following restrictions: the I/O pins SDA and SCL are
mapped to are not “true” open-drain. When configured as open-drain, the PMOS connected
between the I/O pin and V
DD
is disabled, but is still present.
The I
2
C characteristics are described in
Refer also to
for more details on the input/output alternate function characteristics (SDA
and SCL).
Table 39.
Symbol
t
w(SCLL)
t
w(SCLH)
t
su(SDA)
t
h(SDA)
t
r(SDA)
t
r(SCL)
t
f(SDA)
t
f(SCL)
t
h(STA)
t
su(STA)
t
su(STO)
t
w(STO:STA)
C
b
I
2
C characteristics
Standard mode I
2
C
(1)
Parameter
Min
SCL clock low time
SCL clock high time
SDA setup time
SDA data hold time
SDA and SCL rise time
SDA and SCL fall time
Start condition hold time
Repeated Start condition
setup time
Stop condition setup time
Stop to Start condition time
(bus free)
Capacitive load for each bus
line
4.0
4.7
4.0
4.7
400
4.7
4.0
250
0
(3)
1000
300
0.6
µs
0.6
0.6
1.3
400
s
s
pF
Max
Min
1.3
µs
0.6
100
0
(4)
20 + 0.1C
b
900
(3)
300
300
ns
Max
Fast mode I
2
C
(1)(2)
Unit
1. Guaranteed by design, not tested in production.
2. f
PCLK1
must be higher than 2 MHz to achieve standard mode I
2
C frequencies. It must be higher than
4 MHz to achieve fast mode I
2
C frequencies. It must be a multiple of 10 MHz to reach the 400 kHz
maximum I2C fast mode clock.
3. The maximum hold time of the Start condition has only to be met if the interface does not stretch the low
period of SCL signal.
4. The device must internally provide a hold time of at least 300ns for the SDA signal in order to bridge the
undefined region of the falling edge of SCL.
Doc ID 13587 Rev 12
65/96
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