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4.4.3 I2C bus
I2C is a serial, 8‐bit oriented data transfer bus for bit rates up to 400kbps in Fast mode. It consists of
two lines, the serial data line I2CDAT and the serial clock line I2CCLK.
The MTX‐3G‐JAVA modem acts as a single master device, e.g. the clock I2CCLK is driven by the
modem. I2CDAT is a bi‐directional line.
Each device connected to the bus is software which is identified by a unique 7‐bit address. Simple
master/slave relationships exist at all times; the modem operates as a master‐transmitter or as a
master‐receiver. The customer application transmits or receives data only at the modem's request.
Signal
I2CCLK
I2CDAT
GND
1. 2C lines are Open Drain. Internal 10kOhm pull‐up resistors are mounted, so there is no need
to fit them to the host application.
2. According to the I2C Bus Specification Version 2.1, a maximum rise time of300ns is permitted
for the fast mode. There is also a maximum VOL=0.4V at 3mA specified.
3. The value of the pull‐up depends on the capacitive load of the whole system (I2C Slave +
lines). The maximum sink current of I2CDAT and I2CCLK is 4mA.
4. If lines are unused, keep pins open
Use the AT^SSPI command or Java class to configure and activate the I2C bus.
The picture below shows the I2C interface is powered from an internal VEXT supply line so the I2C
interface will be properly shut down when the modem enters the Power‐down mode.
www.mtx‐terminals.com
Direction Description
Output
I2C bus clock signal
1234
I/O
I2C data bus
‐
Ground connection
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MTX M2M® by MATRIX ELECTRONICA S.L.U
MTX‐3G‐JAVA Family
1234
2015/10 v1.6
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