ZHCS363L August 2011 – March 2017 TRF7970A
PRODUCTION DATA.
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.
Table 6-53 describes the NFC Target Protocol register.
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 |