CR95HF datasheet(31/63 Pages) STMICROELECTRONICS

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CR95HF

Commands

Doc ID 018669 Rev 8

31/63

5.8.1

Improving RF performance

Adjusting the Modulation Index and Receiver Gain parameters helps adjust application

behavior. These parameters are the two nibbles of the Analog Register Configuration

The default value of these parameters (Table 20) is set by the PROTOCOLSELECT command,

but they can be overwritten using the Write Register (WRREG) command (

0x09). Table 18

and Table 19 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.

How to modify Analog Register Configuration register (ARC_B) values

Use the PROTOCOLSELECT command (

0x02) to select the correct communication

protocol.

For example, to select the ISO/IEC 18092 protocol:

Send PROTOCOLSELECT command:

>>>

0x02020451

CR95HF reply:

<<<

0x0000

Read the Analog Register Configuration register (ARC_B) value.

Write the ARC_B register index at 0x01:

>>>0x0903680001

CR95HF reply:

<<<

0x0000

Read the ARC_B register value:

>>>

0x0803690100

CR95HF reply:

<<<

0x015F

In this example, the ARC_B register value is

0x5F, where “5” is the Modulation

IndexModulation Index and “F” is the Receiver Gain.

Modify the Modulation Index and Receiver Gain values with 0x23.

Write the ARC_B register index:

>>>

0x090468010123

CR95HF reply:

<<<

0x0000

Table 17.

WRREG command description (Modulation Index and Receiver Gain)

Direction

Data

Comments

Example

Host to

CR95HF

0x09

Command code

>>>0x090468010113

Update ARC_B value to 0x13

>>>0x0903680001

Set Analog Register Index to

0x01 (ARC_B) (1)

This command must be executed before reading the ARC_B register (

0x0803690100).

0x03 or

0x04

Length of data

0x68

Analog Register Configuration address

index

0x00

0x01

Flag Increment address or not after Write

command

0x01

Index pointing to the Modulation Index and

Receiver Gain values in ARC_B register

(0x01) (See Section 5.8.1)

0xXX

New value for Modulation Index and

Receiver Gain nibbles (See Section 5.8.1)

CR95HF to

Host

0x00

Result code

<<<0x0000

0x00

Length of data (= RegCount)

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