CRX14_10 Datasheet, PDF (18/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

CRX14 I²C protocol description
Figure 6. I²C bus protocol
SCL
SDA
START
CONDITION
SDA
SDA
INPUT CHANGE
CRX14
STOP
CONDITION
SCL
1
2
3
SDA
MSB
START
CONDITION
7
8
9
ACK
SCL
1
2
3
SDA
MSB
7
8
9
ACK
STOP
CONDITION
AI00792
4.5
I²C memory addressing
To start up communication with the CRX14, the bus master must initiate a START condition.
Then, the bus master sends 8 bits (with the most significant bit first) on the Serial Data line,
SDA. These bits consist of the Device Select Code (7 bits) plus a RW bit.
According to the I²C bus definition, the seven most significant bits of the Device Select Code
are the Device Type Identifier. For the CRX14, these bits are defined as shown in Table 6.
The 8th bit is the Read/Write bit (RW). It is set to ‘1’ for I²C Read, and to ‘0’ for I²C Write
operations.
If the data sent by the bus master matches the Device Select Code of a CRX14 device, the
corresponding device returns an acknowledgment on the SDA bus during the 9^th bit time.
The CRX14 devices whose Device Select Codes do not correspond to the data sent,
generate a No-ACK. They deselect themselves from the bus and go into stand-by mode.
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Doc ID 8880 Rev 4