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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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Detailed Description
Copyright © 2011–2017, Texas Instruments Incorporated
6.15.3.3.10 NFC Target Protocol Register (0x19)
This register is used (when read) to display the bit rate and protocol type when an NFC/RFID
Initiator/Reader is presented. An example use of this scenario would be when the TRF7970A is placed
into card emulation (Type A or Type B) and another TRF7970A or NFC device (polling for other NFC
devices) is presented to the TRF7970A in card emulation mode. The IRQ indicates that a field was
detected (IRQ Status = 0x04) or that Auto SDD has completed (IRQ Status = 0x08, if configured for
AutoSDD).
If Auto SDD is set and 0x04 is returned in IRQ status, then this register can be read out to see which
commands are coming in for gaining knowledge of the polling cycle sequence. Then, when the correct first
matching command (that is, REQA or REQB) is issued from Reader or Initiator, if AutoSDD is set, the IRQ
fires and the IRQ Status is 0x08, indicating completion of the SDD. The next IRQ should return 0x40 as
status, the Register 0x19 can be checked to make sure it is correct value (that is, 0xC9 for Type A at 106
kbps or 0xC5 for Type B at 106 kbps) indicating there are bytes in the FIFO and a read of the FIFO status
indicates how many bytes to read out. For example, after AutoSDD is completed, there are four bytes in
the FIFO, and these should be the RATS command coming in from the reader, which the MCU controlling
the TRF7970A in Card Emulation mode must respond to. If AutoSDD is not set, as another example with
the TRF7970A in ISO/IEC 14443 B Card Emulation mode, then the field detect happens as previously
described and IRQs also fire to indicate RX is complete (0x40). This register must be checked and
compared against case statement structure that is set up for the value of this register to be 0xC5,
indicating that an ISO/IEC 14443 B command at 106 kbps was issued. When this register (0x19) is 0xC5,
then the FIFO Status can be read and should hold a value of 0x03, and when read, be the REQB
command (0x05, 0x00, 0x00); the controlling MCU must respond with the ATQB response. The next steps
for either of these examples follow the relevant portions of the ISO/IEC 14443-3 or -4 standards, then the
NFC Forum specifications, depending on the system use case or application.
describes the NFC Target Protocol register.
Table 6-53. NFC Target Protocol Register (0x19)
Function:
Displays the bit rate and protocol type (active or passive) transmitted by initiator in first command. It also displays the comparator
outputs of both RF level detectors.
Default:
0x00 at POR = H and EN = L. B0 to B4 are automatically reset after MCU continuous read operation. B6 and B7 continuously
display the RF level comparator outputs.
Bit
Name
Function
Description
B7
Rf_h
RF level is above the wake-
up level setting
The wakeup level is defined by bits B0 to B2 in the NFC Target Detection Level
register (0x18)
B6
Rf_l
RF level is above the RF
collision avoidance level
setting
The collision avoidance level is defined by bits B0 – B2 in the register 0x16
(NFC Low Field Detection Level)
B5
Reserved
Reserved
Reserved
B4
FeliCa
1 = FeliCa
0 = ISO/IEC 14443 A
The first initiator command had physical level coding of FeliCa or
ISO/IEC 14443 A
B3
Pas_106
Passive target at 106 kbps
or transponder emulation
The first initiator/reader command was SENS_REQ or ALL_REQ
B2
Pas_14443B
ISO/IEC 14443 B
transponder emulation
The first reader command was ISO/IEC 14443 B
B1
NFCBR1
Bit rate of first received
command
00 = Reserved
01 = 106 kbps
10 = 212 kbps
11 = 424 kbps
B0
NFCBR0
