e5561

The e5561 is a member of the Atmel Wireless &Microcontrollers  IDentification  IC (IDIC) family forapplications where information has to be transmitted con-tactlessly. The IDIC is connected to a tuned LC circuitfor power supply and bidirectional data communication(Read/Write) to a base station. Atmel Wireless &Microcontrollers offers LC circuit and chip assembled inform of a transponder or tag. These units are small, smartand rugged data storage units.

The e5561 is a Read/Write crypto IC for applicationswhich demand higher security levels than standard R/Wtransponder ICs can offer. For that purpose, the e5561 hasan encryption algorithm block which enables a base sta-tion to authenticate the transponder. The base stationtransmits a random number to the e5561. This challengeis encrypted by both IC and base station. The e5561 sendsback the result to the base station for comparison. As bothshould possess the same secret key, the results of this en-tryption are expected to be equal. Any attempt to fake thebase station with a wrong transponder will be recognizedimmediately.

The on-chip 320-bit EEPROM (10 blocks of 32 bits each)can be read and written blockwise by a base station. Twoor four blocks contain the ID code and six memory blocksare used to store the crypto key as well as the read/writeoptions. The crypto key and the ID code can be protectedindividually against overwriting. Likewise, the cryptokey can not be read out.125 kHz is the typical operational frequency of a systemusing the e5561. Two read data rates are programmable.

Reading occurs through damping the incoming RF fieldwith an on-chip load. This damping is detected by thefield-generating base station. Data transmission startsafter power-up with the transmission of the ID code andcontinues as long as the e5561 is powered. Writing iscarried out with Atmel Wireless & Microcontrollers'writing method. To transmit data to the e5561, the basestation has to interrupt the RF for a short time to create afield gap. The information is encoded in the number ofclock cycles between two subsequent gaps.