Datasheet

PN532_C1 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2017. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.6 — 28 November 2017
115436 121 of 222
NXP Semiconductors
PN532/C1
Near Field Communication (NFC) controller
8.6.12 Serial data switch
Two main blocks are implemented in the CIU. A digital block comprising state machines,
coder and decoder logic and an analog block with the modulator and antenna drivers,
receiver and amplifier. The Serial Data Switch is the interface between these two blocks.
The Serial Data Switch can route the interfacing signals to the pins SIGIN and SIGOUT.
SIGOUT and SIGIN are mainly used to enable the NFC-WI/S
2
C interface in the secure IC
to emulate card functionality with the PN532. SIGIN is capable of processing a digital
signal on transfer speeds above 424 kbit/s. SIGOUT pin can also provide a digital signal
that can be used with an additional external circuit to generate transfer speeds at
106 kbit/s, 212 kbit/s, 424 kbit/s and above.
Load modulation is usually performed internally by the CIU, via TX1 and TX2. However, it
is possible to use LOADMOD to drive an external circuitry performing load modulation at
the antenna (see optional circuitry of Figure 51 on page 212
).
The Serial Data Switch is controlled by the registers CIU_TxSel (see Table 217 on
page 162) and CIU_RxSel (see Table 219 on page 163).
8.6.12.1 Serial data switch for driver and loadmod
The following figure shows the serial data switch for pins TX1 and TX2.
SIGIN is in general only used for secure IC communication. If TxMix is set to logic 1 (see
Table 217 on page 162
), the driver pins are simultaneously controlled by SIGIN and the
internal coder.
The following figure shows the serial data switch for the LOADMOD pin.
Fig 39. Serial data switch for TX1 and TX2
Internal
coder
invert if
INVMOD=1
invert if
POLSIGN=0
AND
0
1
00
01
10
11
DriverSel
TxMIX
Envelope
To driver TX1 and TX2
0- -> ModGsN/P
1 -->CWGsN/P
Tristate
1
SIGIN