CRX14_10 Datasheet, PDF (20/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

CRX14 I²C protocol description
Figure 8. I²C polling flowchart using ACK
Radio Frequency
data exchange
in progress
CRX14
START Condition
DEVICE SELECT
CODE with R/W=1
First byte of instruction
with R/W = 1 already
decoded by the CRX14
ReSTART
NO
ACK
returned
YES
Next
NO
operation is
addressing
the CRX14
YES
Proceed to READ
Operation
STOP
STOP
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4.7
CRX14 I²C read operations
To send a Read command, the bus master sends a START condition, followed by a Device
Select Code and the R/W bit set to ’1’.
The CRX14 that corresponds to the Device Select Code acknowledges and outputs the first
data Byte of the addressed register.
To select a specific register, a dummy Write command must first be issued, giving an
address Byte but no data Bytes, as shown in the bottom half of Figure 9. This causes the
new address to be stored in the internal address pointer, for use by the Read command that
immediately follows the dummy Write command.
In the I²C Read mode, the CRX14 may read one or more data Bytes depending on the
selected register. The bus master has to generate an ACK after each data Byte to read all
the register data in a continuous stream. Only the last data Byte should not be followed by
an ACK. The master then terminates the transfer with a STOP condition, as shown in
Figure 9.
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