CR95HF Datasheet, PDF (31/63 Pages) STMicroelectronics – 13.56-MHz multi-protocol contactless transceiver IC with SPI and UART serial access

CR95HF
Commands
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
register (ARC_B).
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.
Table 17. WRREG command description (Modulation Index and Receiver Gain)
Direction Data
Comments
Example
Host to
CR95HF
CR95HF to
Host
0x09 Command code
0x03 or _{Length of data}
0x04
Analog Register Configuration address
0x68 _index
>>>0x090468010113
Update ARC_B value to 0x13
0x00 or
0x01
0x01
Flag Increment address or not after Write
command
Index pointing to the Modulation Index and
Receiver Gain values in ARC_B register
(0x01) (See Section 5.8.1)
>>>0x0903680001
Set Analog Register Index to
0x01 (ARC_B) ⁽¹⁾
New value for Modulation Index and
0xXX _{Receiver Gain nibbles (See Section 5.8.1)}
0x00 Result code
0x00 Length of data (= RegCount)
<<<0x0000
Register written
1. This command must be executed before reading the ARC_B register (0x0803690100).
How to modify Analog Register Configuration register (ARC_B) values
1. Use the PROTOCOLSELECT command (0x02) to select the correct communication
protocol.
For example, to select the ISO/IEC 18092 protocol:
Send PROTOCOLSELECT command:
CR95HF reply:
>>>0x02020451
<<<0x0000
2. Read the Analog Register Configuration register (ARC_B) value.
a) Write the ARC_B register index at 0x01:
CR95HF reply:
>>>0x0903680001
<<<0x0000
b) Read the ARC_B register value:
CR95HF reply:
>>>0x0803690100
<<<0x015F
In this example, the ARC_B register value is 0x5F, where “5” is the Modulation
IndexModulation Index and “F” is the Receiver Gain.
3. Modify the Modulation Index and Receiver Gain values with 0x23.
Write the ARC_B register index:
CR95HF reply:
>>>0x090468010123
<<<0x0000
Doc ID 018669 Rev 8
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