AN3955 datasheet(18/68 Pages) STMICROELECTRONICS

18 / 68 page

CR95HF low level layer

AN3955

18/68

Doc ID 022017 Rev 1

4.7

SendRecv function

The CR95HF_SendRecv function sends a SendRecv command. The CR95HF encodes the

frame, transmits it at 13.56 MHz, and decodes the contactless tag response.

The contactless tag response is then sent back in the pResponse parameter.

The Parameters input depends on the selected protocol. This application note applies to

ISO/IEC 14443-3 Type A and ISO/IEC 14443-3 Type B products.

Table 10 describes the SendRecv command in ISO/IEC 14443-3 Type A case.

Table 10.

SendRecv command in ISO/IEC 14443-3 Type A case

Table 9.

CR95HF_SendRecv function description

Prototype

result = int8_t CR95HF_SendRecv (uc8

Length,uc8 *Parameters,uint8_t *pResponse)

Input parameter

Length: Number of bytes in Parameters input

Parameters input: Pointer to data

Output parameter

pResponse : Pointer to CR95HF response

Return parameter

CR95HF_ERRORCODE_PARAMETER: Function failed

CR95HF_SUCCESS_CODE: Function is successful.

CR95HF_ERRORCODE_PARAMETERLENGTH: Parameter

length is incorrect.

Parameter name

Byte

Bit

Value

Comments

Example

Command Code

7:0

0x04

REQA command:

0x04022607

with

26:

Data (REQA

command code)

07:

number

of significant bits

(REQA is coded on 7

bits)

Length

7:0

0xXX

Number of Data

bytes and

transmission flag

Data

2:X

7:0

0xXX

Data

Transmission flag

X+1

-RFU

0b0

Split frame

1: CR95HF

appends CRC

0: CR95HF

does not

append CRC

Append CRC

0b0

RFU

3:0

0xX

Number of

significant bits

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