Register Description - Texas Instruments TRF7970A Instruction Manual

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6.13.1.16 Receiver Gain Adjust (0x1A)
This command should be executed when the MCU determines that no TAG response is coming and when
the RF and receivers are switched ON. When this command is received, the reader observes the digitized
receiver output. If more than two edges are observed in 100 ms, the window comparator voltage is
increased. The procedure is repeated until the number of edges (changes of logical state) of the digitized
reception signal is less than 2 (in 100 ms). The command can reduce the input sensitivity in 5-dB
increments up to 15 dB. This command ensures better operation in a noisy environment. The gain setting
is reset to maximum gain at EN = 0 and POR = 1.

6.14 Register Description

6.14.1 Register Preset
After power-up and the EN pin low-to-high transition, the reader is in the default mode. The default
configuration is ISO15693, single subcarrier, high data rate, 1-out-of-4 operation. The low-level option
registers (0x02 to 0x0B) are automatically set to adapt the circuitry optimally to the appropriate protocol
parameters. When entering another protocol (by writing to the ISO Control register 0x01), the low-level
option registers (0x02 to 0x0B) are automatically configured to the new protocol parameters. After
selecting the protocol, it is possible to change some low-level register contents if needed. However,
changing to another protocol and then back, reloads the default settings, and so then the custom settings
must be reloaded.
The Clo0 and Clo1 register (0x09) bits, which define the microcontroller frequency available on the
SYS_CLK pin, are the only two bits in the configuration registers that are not cleared during protocol
selection.
6.14.2 Register Overview
Address
Main Control Registers
0x00
0x01
Protocol Sub-Setting Registers
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x10
0x11
0x14
0x15
0x16
0x17
0x18
Copyright © 2011–2014, Texas Instruments Incorporated
Table 6-24. Register Definitions
Register
Chip Status Control
ISO Control
ISO14443B TX options
ISO14443A high bit rate options
TX timer setting, H-byte
TX timer setting, L-byte
TX pulse-length control
RX no response wait
RX wait time
Modulator and SYS_CLK control
RX Special Setting
Regulator and I/O control
Special Function Register, Preset 0x00
Special Function Register, Preset 0x00
Adjustable FIFO IRQ Levels Register
Reserved
NFC Low Field Detection Level
NFCID1 Number (up to 10 bytes wide)
NFC Target Detection Level
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Product Folder Links: TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
W
R/W
Detailed Description
TRF7970A
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