Datasheet
PN512 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2016. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 5.2 — 16 June 2016
111352 84 of 137
NXP Semiconductors
PN512
Full NFC Forum-compliant frontend
11. Analog interface and contactless UART
11.1 General
The integrated contactless UART supports the external host online with framing and error
checking of the protocol requirements up to 848 kBd. An external circuit can be connected
to the communication interface pins MFIN and MFOUT to modulate and demodulate the
data.
The contactless UART handles the protocol requirements for the communication
protocols in cooperation with the host. Protocol handling generates bit and byte-oriented
framing. In addition, it handles error detection such as parity and CRC, based on the
various supported contactless communication protocols.
Remark: The size and tuning of the antenna and the power supply voltage have an
important impact on the achievable operating distance.
11.2 TX driver
The signal on pins TX1 and TX2 is the 13.56 MHz energy carrier modulated by an
envelope signal. It can be used to drive an antenna directly using a few passive
components for matching and filtering; see Section 14 on page 96
. The signal on pins TX1
and TX2 can be configured using the TxControlReg register; see Section 8.2.2.5 on
page 40.
The modulation index can be set by adjusting the impedance of the drivers. The
impedance of the p-driver can be configured using registers CWGsPReg and
ModGsPReg. The impedance of the n-driver can be configured using the GsNReg
register. The modulation index also depends on the antenna design and tuning.
The TxModeReg and TxSelReg registers control the data rate and framing during
transmission and the antenna driver setting to support the different requirements at the
different modes and transfer speeds.
[1] X = Do not care.
Table 153. Register and bit settings controlling the signal on pin TX1
Bit
Tx1RFEn
Bit
Force
100ASK
Bit
InvTx1RFOn
Bit
InvTx1RFOff
Envelope Pin
TX1
GSPMos GSNMos Remarks
0X
[1]
X
[1]
X
[1]
X
[1]
X
[1]
CWGsNOff CWGsNOff not specified if RF is
switched off
100 X
[1]
0 RF pMod nMod 100 % ASK: pin TX1
pulled to logic 0,
independent of the
InvTx1RFOff bit
1RFpCWnCW
01 X
[1]
0 RF pMod nMod
1RFpCWnCW
11 X
[1]
0 0 pMod nMod
1RF_npCWnCW