AS3910-BQFP AMSCO [austriamicrosystems AG], AS3910-BQFP Datasheet - Page 22

• Manufacturer Part Number: AS3910-BQFP
• Description: 13.56 MHz RFID Reader IC, ISO-14443 A/B
• Manufacturer: AMSCO [austriamicrosystems AG]

AS3910
Data Sheet - A p p l i c a t i o n I n f o r m a t i o n
8.10.5 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 Receiver on
page 13)
is forced to low, processing of the receiver output by the framing block is disabled, all received modulation is rejected. This command is
useful to block 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).
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 framing block is enabled. A common use of this command is to enable again the receiver operation after it was disabled by
the command Mask Receive Data.
Another possible use is in case one wants that the receive processing starts immediately after the transmit command (usually the receiver
operation is enabled 40 µs after the transmission is terminated). This is accomplished by sending the Unmask Receive Data immediately after
the end of transmission interrupt is received.
The command Unmask Receive Data has to be used in the NFC target mode. The sequence implemented in the AS3910 supposes that every
action is started with a transmit command, after sending the transmit data, the receive mode is automatically entered to process the response.
Such a sequence is always in place in case of the ISO-14443 reader mode and also in case of the NFCIP mode where the AS3910 is the
initiator. In case of the NFC target mode this sequence is started by receiving the interrogator request. After the interrupt caused by the first
initiator request command Unmask Receive Data is sent to force the AS3910 in receive mode.
The commands Mask Receive Data and Unmask Receive Data are only accepted when the Receiver is operating.
8.10.6 AD Convert
A/D conversion of signal on AD_IN pin is performed; result is stored in A/D Converter Output Register
(see A/D Converter on page
14).
Duration time: 42µs max.
This command is accepted in any mode where the oscillator and regulators are running.
8.10.7 Measure RF
This command measures the amplitude on the RFI inputs and stores result in the A/D Converter Output Register (see also A/D Converter and
Amplitude Detector on page 15).
When this command is executed 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 13.02mVpp on the RFI
inputs, a 3Vpp signal which is maximum allowed level on each of the two RFI inputs results in 1.8V output DC voltage and would produce the
value of 1110 0110 on the A/D converter output.
Duration time: 42μs max.
This command is accepted in any mode where the oscillator and regulators are running.
8.10.8 Squelch
This direct command is intended to avoid demodulation problems of transponders which produce a lot of noise during data processing (while
data sent by reader is processed and answer prepared). It can also be used in a noisy environment. The operation of this command is explained
in Squelch – refer to page 14.
Duration time: 500μs max
This command is only accepted when the Transmitter and Receiver are operating.
8.10.9 Clear Squelch
Clears the gain reduction which was established by sending Squelch command.
This command is accepted in any mode.
8.10.10 Adjust Regulators
When this command is sent the power supply level of VDD is measured in maximum load conditions and the regulated voltage reference is set
250 mV below this measured level to assure maximum possible stable regulated supply
(see Power Supply, Regulators on page
16). Using this
command increases the system PSSR.
At the beginning of execution of this command, both the receiver and transmitter are switched on to have the maximum current consumption, the
regulators are set to the maximum 3.4V regulated voltage. After 300μs VSP_RF is compared to VDD, in case VSP_RF is not at least 250mV
lower the regulator setting is reduced for one step (100mV) and measurement is done after 300μs. Procedure is repeated as long as VSP_RF
drops 250mV below VDD of until minimum regulated voltage (2.4V) is reached.
www.austriamicrosystems.com/HF_RFID_Reader/AS3910
Revision 2.3
22 - 47