Datasheet
SCL
SDA
data
change
allowed
data
valid
data
change
allowed
data
valid
data
change
allowed
I
2
C Compatible Interface
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5.2 Electrical Characteristics of I
2
C
The USB I
2
C board requires 5V from a computer to function correctly. The maximum current that the I
2
C
board will draw from the computer is 500 mA. This I
2
C board will function within the temperature range of
0°C ≤ T
A
≤ 70°C.
For further information about the devices on the I
2
C board, refer to the following links:
COP8CBE9/CCE9 8-Bit CMOS Flash Microcontroller with 8k Memory, Virtual EEPROM, 10- Bit A/D and
Brownout Reset (SNOS978)
150-mA Low-Noise, Low-Dropout Regulator With Shutdown (SLVS522)
6 I
2
C Compatible Interface
6.1 I
2
C Signals
In I
2
C-compatible mode, the SCL pin is used for the I
2
C clock and the SDA pin is used for the I
2
C data.
Each of these signals need a pull-up resistor according to I
2
C specification. The values of the pull-up
resistors are determined by the capacitance of the bus (typ. ~2k). See I
2
C specification from Phillips for
further details. Signal timing specifications are according to the I
2
C bus specification. Maximum frequency
is 400 KHz.
6.2 I
2
C Data Validity
The data on SDA line must be stable during the HIGH period of the clock signal (SCL). In other words,
state of the data line can only be changed when CLK is LOW.
Figure 3. I
2
C Signals: Data Validity
6.3 I
2
C Start and Stop Conditions
START and STOP bits signify the beginning and the end of the I
2
C session. START condition is defined
as SDA signal transitioning from HIGH to LOW while SCL line is HIGH. STOP condition is defined as the
SDA transitioning from LOW to HIGH while SCL is HIGH. The I
2
C master always generates START and
STOP bits. The I
2
C bus is considered busy after START condition and free after STOP condition. During
data transmission, I
2
C master can generate repeated START conditions. First START and repeated
START conditions are equivalent, function-wise.
4
SNVA343A–April 2008–Revised April 2013
AN-1840 USB I
2
C Interface Board Reference Manual
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