Product data

MFRC631 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.3 — 4 February 2014
227433 32 of 120
NXP Semiconductors
MFRC631
High performance ISO/IEC 14443 A/B reader solution
8.6 Analog interface and contactless UART
8.6.1 General
The integrated contactless UART supports the external host online with framing and error
checking of the protocol requirements up to 848 kbit/s. An external circuit can be
connected to the communication interface pins SIGIN and SIGOUT to modulate and
demodulate the data.
The contactless UART handles the protocol requirements for the communication schemes
in co-operation with the host. The protocol handling itself generates bit- and byte-oriented
framing and handles error detection like Parity and CRC according to the different
contactless communication schemes.
The size, the tuning of the antenna, and the supply voltage of the output drivers have an
impact on the achievable field strength. The operating distance between reader and card
depends additionally on the type of card used.
8.6.2 TX transmitter
The signal delivered on pin TX1 and pin TX2 is the 13.56 MHz carrier modulated by an
envelope signal for energy and data transmission. It can be used to drive an antenna
directly, using a few passive components for matching and filtering, see Section 14
“Application information”. The signal on TX1 and TX2 can be configured by the register
DrvMode, see Section 9.8.1 “
TxMode”.
The modulation index can be set by the TxAmp.
Following figure shows the general relations during modulation
Note: When changing the continuous carrier amplitude, the residual carrier amplitude also
changes, while the modulation index remains the same.
Fig 22. General dependences of modulation
001aan355
time
influenced by set_clk_mode envelope
TX ASK100
1: Defined by set_cw_amplitude.
2: Defined by set_residual_carrier.
TX ASK10
(1)
(2)