CR14 datasheet(13/46 Pages) STMICROELECTRONICS

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CR14

3 CR14 registers

13/46

3.1

Parameter Register (00h)

The Parameter Register is an 8-bit volatile register used to configure the CR14, and thus, to

customize the circuit behavior. The Parameter Register is located at the I²C address 00h and it

is accessible in I²C Read and Write modes. Its default value, 00h, puts the CR14 in standard

ISO14443 type-B configuration.

Table 3.

Parameter Register Bits Description

3.2

Input/Output Frame Register (01h)

The Input/Output Frame Register is a 36-Byte buffer that is accessed serially from Byte 0

through to Byte 35 (see Table 4). It is located at the I²C address 01h.

The Input/Output Frame Register is the buffer in which the CR14 stores the data Bytes of the

request frame to be sent to the PICC. It automatically stores the data Bytes of the answer frame

received from the PICC. The first Byte (Byte 0) of the Input/Output Frame Register is used to

store the frame length for both transmission and reception.

When accessed in I²C Write mode , the register stores the request frame Bytes that are to be

transmitted to the PICC. Byte 0 must be set with the request frame length (in Bytes) and the

frame is stored from Byte 1 onwards. At the end of the transmission, the 16-bit CRC is

automatically added. After the transmission, the CR14 wait for the PICC to send back an

answer frame. When correctly decoded, the PICC answer frame Bytes are stored in the Input/

Output Frame Register from Byte 1 onwards. Byte 0 stores the number of Bytes received from

the PICC.

When accessed in I²C Read mode, the Input/Output Register sends back the last PICC answer

frame Bytes, if any, with Byte 0 transmitted first. The 16-bit CRC is not stored, and it is not sent

back on the I²C bus.

Bit

Control

Value

Description

Frame Standard

ISO14443 type-B frame management

RFU(1)

RFU = Reserved for Future Use.

RFU

Not used

Answer Frame Format

Answer PICC Frames are delimited by SOF and EOF

Answer PICC Frames do not provide SOF and EOF delimiters

ASK Modulation Depth

10% ASK modulation depth mode

1RFU

Carrier Frequency

13.56MHz carrier on RF OUT is OFF

13.56MHz carrier on RF OUT is ON

tWDG

Answer delay watchdog

b5=0, b6=0: Watchdog time-out = 500µs to be used for read

b5=0, b6=1: Watchdog time-out = 5ms to be used for read

b5=1, b6=0: Watchdog time-out = 10ms to be used for write

b5=1, b6=1: Watchdog time-out = 309ms to be used for MCU timings

RFU

Not used

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