AS3955 datasheet(23/111 Pages) AMSCO

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[v1-01] 2015-Apr-29

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AS3955 − Detailed Description

Coding of SENS_RES, SEL_REQ, ACK and NACK

Several bits in certain responses are defined as don’t-care in the

NFC-A standard [NFC Digital], some others are defined by

optional choices in standard protocol. This chapter defines how

these bits are actually set in AS3955.

SENS_RES Response

SENS_RES is a response on ALL_REQ and SENS_REQ commands.

The SENS_RES is defined by Configuration Bytes SENSR1 and

SENSR2 stored in EEPROM.

Figure 21:

Coding of SENS_RES Response

SEL_RES Response, Cascade Level 1 and 2

SEL_RES is the response to SEL_REQ command. Since AS3955

UID is double sized, SEL_RES responses for Cascade Level 1 and

Cascade Level 2 are defined. SEL_RES on Cascade Level 1 and 2

is defined with Configuration Byte SELR except for cascade bit

3. The response on Cascade Level 2 is also configured by

selr_b6_inv bit which, when set, inverts cascade bit 6 in SEL_RES

response on Cascade Level 2 (see IC_CFG2).

Figure 22:

SEL_RES CL1 Coding

Figure 23:

SEL_RES CL2 Coding

Note(s) and/or Footnote(s):

1. According to [ISO14443-3], all bits except b3 are “don’t care” for Cascade Level 1, and all bits except b6 and b3 are “don’t care” for

Cascade Level 2. Bit b6 in CL2 indicates whether the tag is compliant to [ISO14443] or not (resp. b6=1 and b6=0). In case of applications

requiring EMVCo compliance, bit b6 in Cascade Level 1 shall be set as bit b6 in Cascade Level 2 ([EMVCO-1]).

b15

b14

b13

b12

b11

b10

SENSR2

SENSR1

MSB

LSB

Description

sel_res<7:3>

sel_res<1:0>

Cascade bit set: UID not complete

MSB

LSB

Description

sel_res<7:6>

sel_res<5>

sel_res<4:3>

sel_res<1:0>

selr_b6_inv set to 0

NOT sel_res<5>

selr_b6_inv set to 1

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