AS3909 datasheet(54/77 Pages) AMSCO

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AS3909/AS3910 – 54

ams Datasheet, Confidential: 2013-Oct [3-02]

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

Typical Operating Sequence

At power up the AS3909/10 enters in the Stand-by mode.

Content of all registers is set to the default state which is in most

cases 0.

• First action of the microcontroller after a power-up should

be to load the ISO Mode Definition Register and the

configuration registers to configure reader operation.

• Since the regulators are by default set to the maximum

3.4V, which means that they are at supply voltages lower

than 3.4V transparent, it is advised to send the direct

command Adjust Regulators to improve the system PSRR.

• In case the LC tank trimming is implemented the direct

command Calibrate Antenna has to be sent.

• In case the AM modulation will be used (ISO-14443B for

example) setting the modulation depth in the Modulation

Depth Definition Register and sending the command

Calibrate Modulation Depth is suggested next.

After the sequence of events mentioned above the AS3909/10

is ready to operate.

ISO-14443 Reader Operation

First the Ready mode has to be entered by setting the en bit of

the Operation Control Register (address #01 or asserting pin EN).

In this mode the oscillator is started and the regulators are

enabled. When the oscillator operation is stable an interrupt is

sent. Before sending any command to a transponder the

transmitter and receiver have to be enabled by setting the bits

rx_en and tx_en.

In case REQA or WUPA has to be sent, then it is simply done by

sending the appropriate direct command. Or else, the following

sequence has to be followed:

Send the direct command Clear

Define the number of transmitted bytes in the registers

0B and 0C

Write the bytes to be transmitted in the FIFO

Send the direct command Transmit with CRC or Transmit

without CRC (whichever is appropriate)

When all the data is transmitted, an interrupt is sent to

inform the microcontroller that the transmission is

finished (INTR due to end of transmission).

After the transmission is executed, the AS3909/10 receiver

automatically starts to observe the RFI inputs to detect a

transponder response. The RSSI and AGC (in case it is enabled)

are started. The framing block processes the subcarrier signal

from receiver and fills the FIFO with data. When the reception

is finished and all the data is in the FIFO an interrupt is sent to

the microcontroller (INTR due to end of receive), additionally

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