User's Manual

TRF7970A
SLOS743K –AUGUST 2011–REVISED APRIL 2014 www.ti.com
6.14.3.3.3 RSSI Levels and Oscillator Status Register (0x0F)
Table 6-47. RSSI Levels and Oscillator Status Register (0x0F)
Function: Displays the signal strength on both reception channels and RF amplitude during RF-off state. The RSSI values are valid from
reception start till start of next transmission.
Bit Name Function Description
B7 Unused
Crystal oscillator stable
B6 osc_ok 13.56-MHz frequency stable (≈200 µs)
indicator
MSB RSSI value of auxiliary
B5 rssi_x2
Auxiliary channel is by default RX_IN2. The input can be swapped by B3 = 1
RX (RX_IN2)
(Chip State Control register 0x00). If "swapped", the Auxiliary channel is
B4 rssi_x1 Auxiliary channel RSSI
connected to RX_IN1 and, hence, the Auxiliary RSSI represents the signal level
MSB RSSI value of auxiliary
at RX_IN2.
B3 rssi_x0
RX (RX_IN2)
MSB RSSI value of main
B2 rssi_2
RX (RX_IN1)
Active channel is default and can be set with option bit B3 = 0 of chip state
B1 rssi_1 Main channel RSSI
control register 0x00.
LSB RSSI value of main RX
B0 rssi_0
(RX_IN1)
RSSI measurement block is measuring the demodulated envelope signal (except in case of direct
command for RF amplitude measurement described later in direct commands section). The measuring
system is latching the peak value, so the RSSI level can be read after the end of receive packet. The
RSSI value is reset during next transmit action of the reader, so the new tag response level can be
measured. The RSSI levels calculated to the RF_IN1 and RF_IN2 are presented in Section 6.5.1.1 and
Section 6.5.1.2. The RSSI has 7 steps (3 bits) with 4-dB increment. The input level is the peak to peak
modulation level of RF signal measured on one side envelope (positive or negative).
6.14.3.3.4 Special Functions Register (0x10)
Table 6-48. Special Functions Register (0x10)
Function: User configurable options for ISO14443A specific operations
Bit Name Function Description
B7 Reserved Reserved
B6 Reserved Reserved
Disables parity checking for
B5 par43
ISO14443A
0 = 18.88 µs
B4 next_slot_37us Sets the time grid for next slot command in ISO15693
1 = 37.77 µs
Bit stream transmit for Enables direct mode for transmitting ISO14443A data, bypassing the FIFO and
B3 Sp_dir_mode
MIFARE at 106 kbps feeding the data bit stream directly onto the encoder.
0 = normal receive Enable 4-bit replay for example, ACK, NACK used by some cards; for example,
B2 4_bit_RX
1 = 4-bit receive MIFARE Ultralight
0 = anticollision framing
(0x93, 0x95, 0x97) Disable anticollision frames for 14443A (this bit should be set to 1 after
B1 14_anticoll
1 = normal framing (no anticollision is finished)
broken bytes)
0 = 7 subcarrier pulses Selects the number of subcarrier pulses that trigger collision error in the
B0 col_7_6
1 = 6 subcarrier pulses 14443A - 106 kbps
68 Detailed Description Copyright © 2011–2014, Texas Instruments Incorporated
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