TRF7970A_14 Datasheet, PDF (54/87 Pages) Texas Instruments – Multiprotocol Fully Integrated 13.56-MHz RFID and Near Field Communication (NFC) Transceiver IC

TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
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the external system (MCU), so the external system can stop this by putting the receive decoders in reset
mode. The reset mode can be terminated in two ways. The external system can send the enable receiver
command. The reset mode is also automatically terminated at the end of a TX operation. The receiver can
stay in reset after end of TX if the RX wait time register (0x08) is set. In this case, the receiver is enabled
at the end of the wait time following the transmit operation.
6.13.1.13 Enable Receiver (0x17)
This command clears the reset mode in the digital part of the receiver if the reset mode was entered by
the block receiver command.
6.13.1.14 Test Internal RF (RSSI at RX Input With TX ON) (0x18)
The level of the RF carrier at RF_IN1 and RF_IN2 inputs is measured. Operating range between 300 mV_P
and 2.1 V_P (step size is 300 mV). The two values are displayed in the RSSI levels register (0x0F). The
command is intended for diagnostic purposes to set correct RF_IN levels. Optimum RFIN input level is
approximately 1.6 V_P or code 5 to 6. The nominal relationship between the RF peak level and RSSI code
is shown in Table 6-22 and in Section 6.5.1.1.
NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by Enable RX command. The Check RF
commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-22. Test Internal RF Peak Level to RSSI Codes
RF_IN1 [mV_PP]
Decimal Code
Binary Code
300
600
900
1200
1500
1800
1
2
3
4
5
6
001
010
011
001
101
011
2100
7
111
6.13.1.15 Test External RF (RSSI at RX Input with TX OFF) (0x19)
This command can be used in active mode when the RF receiver is switched on but RF output is switched
off. This means bit B1 = 1 in Chip Status Control Register. The level of RF signal received on the antenna
is measured and displayed in the RSSI Levels register (0x0F). The relation between the 3 bit code and the
external RF field strength [A/m] must be determinate by calculation or by experiments for each antenna
type as the antenna Q and connection to the RF input influence the result. The nominal relation between
the RF peak to peak voltage in the RF_IN1 input and RSSI code is shown in Table 6-23 and in
Section 6.5.1.2.
NOTE
If the command is executed immediately after power-up and before any communication with
a tag is performed, the command must be preceded by an Enable RX command. The Check
RF commands require full operation, so the receiver must be activated by Enable RX or by a
normal Tag communication for the Check RF command to work properly.
Table 6-23. Test External RF Peak Level to RSSI Codes
RF_IN1 [mV_PP]
Decimal Code
Binary Code
40
60
80
100
140
180
300
1
2
3
4
5
6
7
001
010
011
001
101
011
111
54
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