MFRC522 datasheet(63/109 Pages) NXP

63 / 109 page

112132

Product data sheet

Rev. 3.2 — 22 May 2007

63 of 109

NXP Semiconductors

MFRC522

Contactless Reader IC

11.3 Serial Data Switch

Two main blocks are implemented in the MFRC522. A digital circuitry, comprising state

machines, coder and decoder logic and an analog circuitry with the modulator and

antenna drivers, receiver and amplification circuitry. For example, the interface between

these two blocks can be configured in the way, that the interfacing signals may be routed

to the pins MFIN and MFOUT.

This topology supports, that the analog part of the MFRC522 may be connected to the

digital part of another device.

The serial signal switch is controlled by the register TxSelReg and RxSelReg.

The following figure shows the serial data switch for TX1 and TX2.

11.4 MFIN/MFOUT interface support

The MFRC522 is basically divided into digital circuitry and analog circuitry. The digital

circuitry contains state machines, coder and decoder logic and so on and the analog

circuitry contains the modulator and antenna drivers, receiver and amplification circuitry.

The interface between these two blocks can be configured in the way, that the interfacing

signals may be routed to the pins MFIN and MFOUT (see Figure 21 “Overview

MFIN/MFOUT Signal Routing”). The configuration is done by bits MFOutSel, DriverSel

and UARTSel of registers TxSelReg and RxSelReg.

This topology supports, that some parts of the analog part of the MFRC522 may be

connected to the digital part of another device.

The switch MFOutSel in register TxSelReg can be used to measure MIFARE® and

ISO/IEC14443 related signals. This is especially important during the design In phase or

for test purposes to check the transmitted and received data.

However, the most important use of MFIN/MFOUT pins is the active antenna concept. An

external active antenna circuit can be connected to the digital circuit of the MFRC522.

MFOutSel has to be configured in that way that the signal of the internal Miller Coder is

send to MFOUT pin (MFOutSel = 4). UARTSel has to be configured to receive

Manchester signal with sub-carrier from MFIN pin (UARTSel = 1).

It is possible, to connect a 'passive antenna' to pins TX1, TX2 and RX (via the appropriate

filter and matching circuit) and at the same time an Active Antenna to the pins MFOUT

and MFIN. In this configuration, two RF-parts may be driven (one after another) by one

host processor.

Fig 20. Serial data switch for TX1 and TX2.

MFIN

invert if

PolMfin =0

internal

Coder

To driver TX1 and TX2

0 = impedance = MOD

1 = inpedance = CW

invert if

InvMod=1

Tristate

DriverSel

Envelope

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