PCF7936AS3851 datasheet(7/32 Pages) PHILIPS

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NXP Semiconductors

Product Specification

Security Transponder (HITAG2)

PCF7936AS

2010 May 04

CONFIDENTIAL

FUNCTIONAL DESCRIPTION SECURITY

TRANSPONDER

The PCF7936AS does not require any additional power

supply. It derives its power supply by inductive coupling to

the LF Field, which is generated by the basestation.

Reading and writing to the transponder is provided by

amplitude modulation of the LF field.

The Contactless Interface generates the chip power supply,

clock

and

reset

and

features

the

modulator,

and

demodulator. The system clock is derived from the LF field

generated by the basestation that typically operates with a

carrier frequency of 125 kHz.

The Control Logic incorporates the data acquisition logic to

enable communication with the transponder and the

memory access control logic. Access to the transponder

memory (EEPROM) depends on the device configuration

and the authentication state. The memory is split into

blocks and pages with independent access rights, as

configured by the user and partly predefined by design.

Device authentication may be performed in Password

mode or in Ciphered mode. In Password mode the

basestation and transponder in plain exchange a set of

passwords, while in Cipher mode a mutual authentication

based on a security algorithm is performed that employs a

Secret Key and a random number. The security algorithm is

determined by the on-chip Calculation Unit that in addition

supports ciphered communication and data exchange

between the basestation and the transponder.

The Cipher mode is ideally suited for vehicle immobilization

application.

Transponder operation and authentication is controlled by

commands send form the basestation, while in Read Only

mode data transmission commences after device reset and

a time-out condition.

7.1 Memory Organization, EEPROM

The device incorporates 256 bit of non-volatile memory

(EEPROM) that is organized as 8 pages with 32 bit per

page, referred to as Transponder Memory, TM. The

Transponder

Memory,

TM,

split

into

areas

for

Transponder Configuration/Personalization, TCFG, and

User Memory, USER, see Figure 3.

Page 0

Page 7

TCFG

Page 4

Page 3

USER

Transponder Memory, TM

Figure 3. Memory Organization

The TM segment can be accessed only, after successful

device

authorization.

Depending

the

device

configuration, device authorization is performed either in

Password mode or in Cipher mode. Subsequent memory

access is provided only in accordance with the memory

protection settings applied.

Any

changes

made

regarding

the

Transponder

Configuration, TCFG, respectively Page 1 to 3, become

effective after a device reset or initialization sequence only.

The

organization

the

Transponder

Memory,

TM,

depends on the authorization method selected (Password

or Cipher mode) by the corresponding configuration bit

(ENC) see Figure 4.

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