CRX14_10 Datasheet, PDF (22/47 Pages) STMicroelectronics – ISO14443 type-B contactless coupler chip with anti-collision, CRC management and anti-clone function

Applying the I²C protocol to the CRX14 registers
CRX14
5
Applying the I²C protocol to the CRX14 registers
5.1
I²C parameter register protocol
Figure 10 shows how new data is written to the Parameter Register. The new value
becomes active after the I²C STOP condition.
Figure 11 shows how to read the Parameter Register contents. The CRX14 sends and re-
sends the Parameter Register contents until it receives a NoACK from the I²C Host.
The CRX14 supports the I²C Current Address and Random Address Read modes. The
Current Address Read mode can be used if the previous command was issued to the
register where the Read is to take place.
Figure 10. Host-to-CRX14 transfer: I²C write to parameter register
S
T
Bus Master
A
R
T
R/W
Device Select
Code
Parameter Register
Address
S
Register Byte
T
Value
O
P
CRX14 Write
1 0 1 0X X X
00h
data
Bus Slave
ACK
ACK
ACK
ai09240
Figure 11. CRX14-to-host transfer: I²C random address read from parameter register
R
E
S
R/W
T
S
T
R/W
Bus Master ^A
R
T
Device Select
Code
Parameter Register ^A Device Select
Address
R
Code
T
NoACK
S
T
O
P
CRX14 Read
1 0 1 0X X X
00h
1 0 1 0X X X
data
Bus Slave
ACK
ACK
Register Byte
ACK
Value
ai09241
Figure 12. CRX14-to-host transfer: I²C current address read from parameter register
Bus Master
CRX14 Read
Bus Slave
S
R/W
T
A _{Device Select}
R
Code
T
NoACK
S
T
O
P
1 0 1 0X X X
data
ACK
Register Byte
Value
ai09242
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Doc ID 8880 Rev 4