AS3911B datasheet(56/155 Pages) AMSCO

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AS3911B – 56

ams Datasheet: 2014-Jun-12 [v1-08]

A p pl i c at io n I n f o r m at i o n

Mask Receive Data and Unmask Receive Data

After the direct command Mask Receive Data the signal rx_on,

which enables the RSSI and AGC operation of the Receiver (see

also Receiver) is forced to low, processing of the receiver output

by the receive data framing block is disabled. This command is

useful to mask receiver and receive framing from processing

the data when there is actually no input and only a noise would

be processed (for example in case where a transponder

processing time after receiving a command from the reader is

long). Masking of receive is also possible using Mask Receive

Timer. Actual masking is a logical or of the two mask receive

processes.

The direct command Unmask Receive Data is enabling normal

processing of the received data (signal rx_on is set high to

enable the RSSI and AGC operation), the receive data framing

block is enabled. A common use of this command is to enable

again the receiver operation after it was masked by the

command Mask Receive Data. In case Mask Receive Timer is

running while command Unmask Receive Data is received,

reception is enabled, Mask Receive Timer is reset.

The commands Mask Receive Data and Unmask Receive Data

are only accepted when the Receiver is enabled (bit rx_en is set).

Direct command chaining is possible.

IRQ due to termination of direct command is not produced.

Measure Amplitude

This command measures the amplitude on the RFI inputs and

stores result in the A/D Converter Output Register.

When this command is executed the Transmitter and Amplitude

Detector are enabled, the output of the Amplitude Detector is

multiplexed to the A/D Converter input (the A/D Converter is

in absolute mode). The Amplitude Detector conversion gain is

0.6 VINPP/ VOUT. One LSB of the A/D converter output represents

13.02 mVpp on the RFI inputs. A 3 Vpp signal, which is maximum

allowed level on each of the two RFI inputs, results in 1.8 V

output DC voltage and would produce a value of 1110 0110b

on the A/D converter output.

Duration time: 25 μs max.

This command is accepted in case en (bit 7 of the Operation

Control Register) is set and Xtal oscillator frequency is stable.

Direct command chaining is not possible.

IRQ due to termination of direct command is produced after

command execution is terminated.

Squelch

This direct command is intended to avoid demodulation

problems of transponders which produce a lot of noise during

data processing. It can also be used in a noisy environment. The

operation of this command is explained in “Squelch” on

page 23.

AS3911B Datasheet(PDF) 56 Page - ams AG

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