User's Manual

SDI011 REFERENCE MANUAL 17
3.5. Contactless communication principles and SDI011
usage recommendations
SDI011 is a dual interface reader capable of reading both contact smart cards and contactless
user tokens. The following paragraph focuses on a few specifics of the contactless
communication to outline usage recommendations in order to ensure best user experience.
SDI011 is a contactless reader
1
designed to
communicate with user tokens.
User tokens
2
are made of a contactless
integrated circuit card connected to an
antenna
User tokens can take several form factors:
 Credit card sized smart card
 Key fob
 NFC mobile phone etc…
Communication between SDI011 and user
tokens uses magnetic field inductive
coupling.
The magnetic field generated by SDI011 has a carrier frequency of 13.56MHz.
3.5.1. Power supply
When the user token is put in the magnetic field of the reader, its antenna couples with the
reader and an induction current appears in the antenna thus providing power to the integrated
circuit. The generated current is proportional to the magnetic flux going through the antenna of
the user token.
3.5.2. Data exchange
The carrier frequency of the magnetic field is used as a fundamental clock signal for the
communication between the reader and the card. It is also used as a fundamental clock input
for the integrated circuit microprocessor to function.
To send data to the user token the reader modulates the amplitude of the field. There are
several amplitude modulation and data encoding rules defined in ISO/IEC 14443. The reader
should refer to the standard for further details.
To answer to the reader, the integrated circuit card of the user token modulates its way of
loading (impedance) the field generated by the reader. Here also further details can be found in
ISO/IEC 14443.
1
In the ISO/IEC 14443 standard, the reader is called the proximity coupling device (PCD)
2
In the ISO/IEC 14443 standard, the user token is called proximity integrated chip card (PICC)