GD32F20x User Manual
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current-source or pull-up resistor. When the bus is free, both lines are HIGH. The output
stages of devices connected to the bus must have an open-drain or open-collect to perform
the wired-AND function. Data on the I2C-bus can be transferred at rates of up to 100 kbit/s in
the standard-mode and up to 400 kbit/s in the fast-mode. Due to the variety of different
technology devices (CMOS, NMOS, bipolar) that can be connected to the I2C-bus, the
voltage
levels of the logical ‘0’ (LOW) and ‘1’ (HIGH) are not fixed and depend on the
associated level of V
DD
.
20.3.2.
Data validation
The data on the SDA line must be stable during the HIGH period of the clock. The HIGH or
LOW state of the data line can only change when the clock signal on the SCL line is LOW
(see
). One clock pulse is generated for each data bit transferred.
Figure 20-2. Data validation
20.3.3.
START and STOP condition
All transactions begin with a START (S) and are terminated by a STOP (P) (see
).A HIGH to LOW transition on the SDA line while SCL is HIGH
defines a START condition. A LOW to HIGH transition on the SDA line while SCL is HIGH
defines a STOP condition.
Figure 20-3. START and STOP condition
SDA
SCL
SDA
SCL
START
STOP
20.3.4.
Clock synchronization
Two masters can begin transmitting on a free bus at the same time and there must be a
method for deciding which master takes control of the bus and complete its transmission. This
SDA
SCL
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...