User's Manual

TRF7970A
www.ti.com SLOS743K –AUGUST 2011–REVISED APRIL 2014
Table 6-15. NFC Target Detection Level Register
Bit Signal Name Function Comments
B7 Id_s1
NFCID1 size used in 106 kbps passive target SDD
B6 Id_s0
Automatic SDD using internal state machine and ID
B5 Sdd_en 1 = Enables internal SDD protocol
stored in NFCID Number register
(1)
B4 N/A
B3 Hi_rf Extended range for RF measurements
B2 Rfdet_h2
RF field level required for system wake-up. If all Comparator output is displayed in NFC Target
B1 Rfdet_h1
bits are 0, the RF level detection is switched off. Protocol register B7 (rf_h)
B0 Rfdet_h0
(1) Refer to the device errata (SLOZ011) for details on automatic SDD dependencies.
Default: reset to 00 at POR on VEXT (not on POR based on V
DD_X
), not reset at EN = 0
Table 6-16. Bits B0 to B3 of the NFC Target Detection Level Register
b0 B1 B2 000 001 010 011 100 101 110 111
B3 = 0 RF Vpp Not active 480 mV 350 mV 250 mV 220 mV 190 mV 180 mV 170 mV
B3 = 1 RF Vpp Not active 1500 mV 700 mV 500 mV 450 mV 400 mV 320 mV 280 mV
When the voltage supply system and the oscillator are started and is stable, the osc_ok goes high (B6 of
RSSI Level and Oscillator Status register) and IRQ is sent with bit B2 = 1 of IRQ register (field change).
Bit B7 NFC Target Protocol in register directly displays the status of RF level detection (running constantly
also during normal operation). This informs the MCU that the chip should start operation as an NFC
TARGET device.
When the first command from the INITIATOR is received another IRQ sent with B6 (RX start) set in IRQ
register. The MCU must set EN = H (confirm the power-up) in the time between the two IRQs as the
internal power-up ends after the second IRQ. The type and coding of the first initiator (or reader in the
case of a tag emulator) command define the communication protocol type which the target must use. So
the communication protocol type is available in the NFC Target Protocol register immediately after
receiving the first command. The coding of the NFC Target Protocol register is described next.
NFC Target Protocol Register (0x19) – displays the bit rate and protocol type (active or passive)
transmitted by initiator in the first command. It also displays the comparator outputs of both RF level
detectors.
Table 6-17. NFC Target Protocol Register
Bit Signal Name Function Comments
The wake-up level is defined by bits b0-b3 of NFC
B7 Rf_h 1 = RF level is above the set wake-up level
Target Detection Level register
1 = RF level is above the RF collision avoidance The collision avoidance level is defined by bits b0-
B6 Rf_l
level. b2 of NFC Low Field Detection Level register
B5 N/A
1 = FeliCa type The first initiator command had physical level
B4 FeliCa
0 = ISO14443A type coding like FeliCa or like ISO14443A
The first initiator/reader command was SENS_REQ
B3 Pas106 Passive target 106 kbps or tag emulation
or ALL_REQ
B2 Pas14443B Tag emulation ISO14443B The first reader command was of ISO14443B type
B1 Nfcbr1 00 = N/A
01 = 106 kbps
Bit rate of first received command
10 = 212 kbps
B0 Nfcbr0
11 = 424 kbps
Copyright © 2011–2014, Texas Instruments Incorporated Detailed Description 49
Submit Documentation Feedback
Product Folder Links: TRF7970A