CR14 STMicroelectronics, CR14 Datasheet - Page 19

• Manufacturer Part Number: CR14
• Description: Low Cost Iso14443 Type-b Contactless Coupler Chip With Anti-collision And Crc Management
• Manufacturer: STMicroelectronics

CR14
4.6
Figure 7.
BUS Master
CR14 WRITE
BUS Slave
CR14 I²C Write Operations
The bus master sends a START condition, followed by a Device Select Code and the R/W bit
set to ’0’. The CR14 that corresponds to the Device Select Code, acknowledges and waits for
the bus master to send the Byte address of the register that is to be written to. After receipt of
the address, the CR14 returns another ACK, and waits for the bus master to send the data
Bytes that are to be written.
In the CR14 I²C Write mode, the bus master may sends one or more data Bytes depending on
the selected register.
The CR14 replies with an ACK after each data Byte received. The bus master terminates the
transfer by generating a STOP condition.
The STOP condition at the end of a Write access to the Input/Output Frame Register causes
the Radio Frequency data exchange between the CR14 and the PICC to be started.
During the Radio Frequency data exchange, the CR14 disconnects itself from the I²C bus. The
time (t
format. To know when the exchange is complete, the bus master uses an ACK polling
sequence as shown in
CR14 I²C Write Mode Sequence
Initial condition: a Radio Frequency data exchange is in progress.
Step 1: the master issues a START condition followed by the first Byte of the new
instruction (Device Select Code plus R/W bit).
Step 2: if the CR14 is busy, no ACK is returned and the master goes back to Step 1. If the
CR14 has completed the Radio Frequency data exchange, it responds with an ACK,
indicating that it is ready to receive the second part of the next instruction (the first Byte of
this instruction being sent during Step 1).
RFEX
DEV SEL
) needed to complete the exchange is not fixed as it depends on the PICC command
R/W
ACK
BYTE ADDR
Figure
8. It consists of the following:
ACK
DATA 1
ACK
DATA 2
ACK
DATA 3
4 CR14 I²C protocol description
ACK
DATA N
ACK
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