AS3911 datasheet(118/149 Pages) AMSCO

118 / 149 page

AS3911 – 118

ams Datasheet, Confidential: 2013-Oct [2-03]

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

Power-up Sequence

At power-up, the AS3911 enters the Power-down mode. The

content of all registers is set to the default state.

Firstly, the microcontroller after a power-up must

correctly configure the two IO configuration registers.

The content of these two registers defines operation

options related to hardware (power supply mode, Xtal

type, use of MCU_CLK clock, antenna operation mode).

Configure the regulators. It is recommended to use

direct command Adjust Regulators to improve the

system PSRR.

If implementing the LC tank tuning, then send the direct

command Calibrate Antenna.

If using the AM modulation (ISO14443B for example),

then set the modulation depth in the AM Modulation

Depth Control Registerand send the command Calibrate

Modulation Depth.

The AS3911 is now ready to operate.

Reader Operation

To begin with, the operation mode and data rate have to be

configured by writing the Mode Definition Register and Bit Rate

Definition Register. Additionally, the receiver and transmitter

operation options related to operation mode have to be

defined. This is done automatically by sending the direct

command Analog Preset. If more options are required apart

from those defined by Analog Preset, then such options must

be additionally set by writing the appropriate registers.

Next, the Ready mode has to be entered by setting the bit en

of the Operation Control Register. 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. RFID protocols usually require that the reader field is

turned on for a while before sending the first command (5 ms

for ISO14443). General purpose timer can be used to count this

time.

In case REQA or WUPA has to be sent this is simply done by

sending appropriate direct command otherwise the following

sequence has to be followed:

Send the direct command Clear

Define the number of transmitted bytes in the Number

of Transmitted Bytes Register 1 and Number of

Transmitted Bytes Register 2

Write the bytes to be transmitted in the FIFO

Send the direct command Transmit With CRC or

Transmit Without CRC (whichever is appropriate)

AS3911 Datasheet(PDF) 118 Page - ams AG

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