EM4056

Copyright

© 2005, EM Microelectronic-Marin SA

9

www.emmicroelectronic.com

Add

Add command to add one 16-bit data word to another 16-bit data word pointed by the specified address, this command

writes the sum at the specified address. It is possible to add a value to an already protected memory location that has been

protected against reading, but not to a memory location that has been protected against writing attempts.

1 bit

4 bits

MSB

8 bits

MSB

16 bits

MSB

8 bits

X8

Reader

Start

Add

Address

Datas

CRC

2 bits

8 bits

X8

Transponder

twp WOk nWOk

CRC

Fig. 14

Comp

Compares a 16 bits data word with another word pointed by the specified address.

It is possible to perform a comparison with a value pointed by a read protected address.

But it is impossible to compare a value with another one in the opaque area without entering the PIN. In the case of PIN

violation, the result of the comparison is always false.

Ega=1, comparison successful.

1 bit

4 bits

MSB

8 bits

MSB

16 bits

MSB

8 bits

X8

Reader

Start

Comp

Address

Datas

CRC

2 bits

8 bits

X8

Transponder

trp

Ega nEga

CRC

Fig. 15

Login

Compares a 16 bit data word with the PIN word at the address 127.

When a PIN comparison is made (Adr 127) and the identity is established, a write operation occurs in the EEPROM, PIN =

CONF , the success bit is released (SUC = 0), the PIN counter is decremented (PIN = PIN - 1) and the corresponding new

value is written in the EEPROM.

After n erroneous attempts (PIN=0), the ALM bit is set (ALM = 1), and written in the EEPROM. Since that moment the entire

memory is irreversibly locked. The unprotected data words (Rp=0) remain accessible for reading the information they are

containing.

1 bit

4 bits

MSB LSB

16 bits

MSB LSB

8 bits

X8

1

Reader

Start

Login

Datas

CRC

4 bits

8 bits

X8

1

Transponder

twp Ega nEga WOk nWOk

CRC

Fig. 16

Ega=1, password ok. Wok=1, writing operation successful.