ST25R95 datasheet(35/61 Pages) STMICROELECTRONICS

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5.11

Write Register (WrReg) command (0x09) description

The Write Register (WrReg) command (0x09) is used to:

•

set the Analog Register Configuration address index value before reading or overwriting the Analog Register

Configuration register (ARC_B) value

•

set the Analog Register Configuration register (ACC_A) value

–

bits [7:6] are ST reserved and must be set to ‘0’

–

bits [5:4] set the demodulator sensitivity (‘00’ = AM 10% or ‘10’ = AM 100%)

–

bits [3:0] set the Load modulation index (‘0001’ = minimum load modulation, ‘0111’ = default value,

‘1111’ = maximum load modulation). The user can adjust this value to better fit its application.

•

set the Timer window (TimerW) value used to improve ST25R95 demodulation when communicating with

ISO/IEC 14443 Type A tags

•

set the AutoDetect Filter used to help synchronization of ST25R95 with FeliCa™ tags

•

configure the HF2RF bit

Note:

When the HF2RF bit is ‘0’, Reader mode is possible (default mode). When set to ‘1’, VPS_TX power

consumption is reduced (Ready mode).

5.11.1

Improving RF performance

Adjusting the Modulation Index and Receiver Gain parameters in reader mode or the Load modulation index and

Demodulator sensitivity parameters in card emulation mode can help to improve application behavior.

Modulation index and receiver gain parameters for reader mode

The default values of these parameters (Table 35. ARC_B default code for available reader protocols) are set by

the ProtocolSelect command, but they can be overwritten using the Write Register (WrReg) command (0x09).

Table 31. Possible modulation index values and Table 32. Possible receiver gain values list possible values for the

Modulation Index and Receiver Gain parameters, respectively.

This new configuration is valid until a new ProtocolSelect or Write Register (of register ARC_B) command is

executed. Register values are cleared at power off.

Table 29. WrReg command description (Modulation index and receiver gain)

Direction

Data

Comments

Example

Host to ST25R95

0x09

Command code

>>>0x090468010113

Update ARC_B value to 0x13

>>>0x0903680001

Set Analog Register Index to 0x01 (ARC_B)(1)

0x03 or

0x04

Length of data

0x68

Analog Register Configuration address index

0x00 or

0x01

Flag Increment address or not after Write

command

0x01

Index pointing to the Modulation Index and

Receiver Gain values in the ARC_B register

(0x01) (see Section 5.11.1 Improving RF

performance)

0xXX

New value for Modulation Index and Receiver

Gain nibbles (see Section 5.11.1 Improving

RF performance)

ST25R95 to Host

0x00

Result code

<<<0x0000

0x00

Length of data

1. This command must be executed before reading the ARC_B register (

0x0803690100).

ST25R95

Write Register (WrReg) command (0x09) description

DS12807 - Rev 4

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