STM32F101X6 datasheet(49/64 Pages) STMICROELECTRONICS

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STM32F101xx

Electrical characteristics

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5.3.15

Communications interfaces

I2C interface characteristics

Unless otherwise specified, the parameters given in Table 34 are derived from tests

performed under ambient temperature, fPCLK1 frequency and VDD supply voltage conditions

summarized in Table 7.

The STM32F101xx access line I2C interface meets the requirements of the standard I2C

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 VDD is disabled, but is still present. In addition, there is a protection

diode between the I/O pin and VDD. As a consequence, when multiple master devices are

connected to the I

2C bus, it is not possible to power off the STM32F101xx while another I2C

master node remains powered on. Otherwise, the ST device would be powered by the

protection diode.

The I2C characteristics are described in Table 34. Refer also to Section 5.3.12: I/O port

characteristics for more details on the input/output alternate function characteristics (SDA

and SCL).

Table 34.

I2C characteristics

Symbol

Parameter

Standard mode I2C(1)

Values based on standard I2C protocol requirement, not tested in production.

Fast mode I2C(1)(2)

fPCLK1 must be higher than 2 MHz to achieve the maximum standard mode I

2C frequency. It must be

higher than 4 MHz to achieve the maximum fast mode I2C frequency.

Unit

Min

Max

Min

Max

tw(SCLL)

SCL clock low time

4.7

1.3

µs

tw(SCLH)

SCL clock high time

4.0

0.6

tsu(SDA)

SDA setup time

250

100

th(SDA)

SDA data hold time

0(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.

0(4)

The device must internally provide a hold time of at least 300 ns for the SDA signal in order to bridge the

undefined region of the falling edge of SCL.

900(3)

tr(SDA)

tr(SCL)

SDA and SCL rise time

1000

20+0.1Cb

300

tf(SDA)

tf(SCL)

SDA and SCL fall time

300

20+0.1Cb

300

th(STA)

Start condition hold time

4.0

0.6

µs

tsu(STA)

Repeated Start condition setup

time

4.7

0.6

tsu(STO)

Stop condition setup time

4.0

0.6

µs

tw(STO:STA)

Stop to Start condition time (bus

free)

4.7

1.3

µs

Capacitive load for each bus line

400

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