Texas Instruments TRF7970A Manual page 55

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6.14.1.10 Delayed Transmission Without CRC (0x12)
Same as Section 6.14.1.9
6.14.1.11 Transmit Next Time Slot (0x14)
When this command is received, the reader transmits the next slot command. The next slot sign is defined
by the protocol selection. This is used by the ISO/IEC 15693 protocol.
6.14.1.12 Block Receiver (0x16)
The block receiver command puts the digital part of receiver (bit decoder and framer) in reset mode. This
is useful in an extremely noisy environment, where the noise level could otherwise cause a constant
switching of the subcarrier input of the digital part of the receiver. The receiver (if not in reset) would try to
catch a SOF signal, and if the noise pattern matched the SOF pattern, an interrupt would be generated,
falsely signaling the start of an RX operation. A constant flow of interrupt requests can be a problem for
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.
6.14.1.13 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.
6.14.1.14 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
and 2.1 V (step size is 300 mV). The two values are displayed in the RSSI Levels and Oscillator Status
P
register (0x0F). The command is intended for diagnostic purposes to set correct RF_IN levels. Optimum
RFIN input level is approximately 1.6 V
level and RSSI code is shown in
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.
RF_IN1 [mV
PP
Decimal Code
Binary Code
6.14.1.15 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 and Oscillator Status 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
Copyright © 2011–2017, Texas Instruments Incorporated
with CRC excluded.
or code 5 to 6. The nominal relationship between the RF peak
P
Table 6-22
Table 6-22. Test Internal RF Peak Level to RSSI Codes
] 300 600
1 2
001 010
Section 6.5.1.2.
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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
and in Section 6.5.1.1.
NOTE
900 1200 1500
3 4 5
011 001 101
TRF7970A
TRF7970A
1800 2100
6 7
011 111
Detailed Description
P
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