AS3956 datasheet(16/107 Pages) AMSCO

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[v1-11] 2018-Nov-14

AS3956 − Detailed Description

Chip Initialization in the Different Power Modes

During chip initialization, values from the EEPROM

configuration bytes are loaded into the configuration registers.

Figure 13:

Chip Initialization in the Different Power Modes

Resetting the AS3956

To fully reset the AS3956 it is necessary to remove all sources

of power:

• Turn off the RF field and

• Take /SS pin high or remove power from the VP_IO line.

Interface Arbitration

Concurrent access to AS3956 internal EEPROM from RF or SPI /

I²C requires arbitration, to resolve conflicts or undesired

behaviour.

Arbitration Mode 0 (first-come-first-serve)

AS3956 arbitrates EEPROM read/write accesses according to

first-come-first-serve principle.

• In case no read/write access is currently ongoing, both RF

and SPI / I²C interfaces are allowed to read/write into

EEPROM.

• In case a read/write request comes over RF, while SPI / I²C

is reading/writing, AS3956 will return a NAK_5 and will

then enter SENSE/SLEEP state. The chip will generate an

I_init IRQ and an EEPROM access error IRQ.

• In case a read/write request comes over SPI / I²C while RF

is reading/writing, AS3956 will trigger a I_err_acc

interrupt (see Figure 93).

• In case a read request comes over SPI / I²C while RF is

reading/writing to the EEPROM, the AS3956 will reply all

zeros over SPI / I²C.

Power Mode

Chip Initialization Occurs When

RF field or external power VP_IO turns on and /SS is low, whichever first.

Power up in PM 0 or 1 first and then switch to PM 3 by command from external

microcontroller when external power is available

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