ISO/IEC 15693, is an ISO/IEC standard for vicinity cards, i.e. cards which can be read from a greater distance as compared with proximity cards. Such cards can normally be read out by a reader without being powered themselves, as the reader will supply the necessary power to the card over the air (wireless).
ISO/IEC 15693 systems operate at the 13.56 MHz frequency, and offer maximum read distance of 1–1.5 meters. As the vicinity cards have to operate at a greater distance, the necessary magnetic field is less (0.15 to 5 A/m) than that for a proximity card (1.5 to 7.5 A/m).
Example applications
Ski pass: each of those has a unique ID and the system knows for how long the pass is valid etc.
2 bits are coded as the position of a 9.44 μs pause in a 75.52 μs symbol time, giving a bit rate of 26.48 kilobits per second. The least-significant bits are sent first.
1 out of 256 pulse-position modulation
8 bits are coded as the position of a 9.44 μs pause in a 4.833 ms symbol time, giving a bit rate of 1.65 kbit/s.
Communication to the reader
The card has two ways to send its data back to the reader. Both use a subcarrier transmitted back to the reader using load modulation.
A logic 0 starts with eight pulses of 423.75 kHz followed by an unmodulated time of 18.88 μs (256/ fc); a logic 1 is the other way round. The data frame delimiters are code violations, a start of frame is:
Frequency-shift keying by switching between a 423.75 kHz sub carrier (operating frequency divided by 32) and a 484.25 kHz sub carrier (operating frequency divided by 28). The data rate can be:
Low 6.67 kbit/s (fc/2032)
High 26.69 kbit/s (fc/508)
A logic 0 starts with eight pulses of 423.75 kHz followed by nine pulses of 484.28 kHz; a logic 1 is the other way round. The data frame delimiters are code violations, a start of frame is:
μController: Texas Instruments offers a small μController entirely powered by the ISO/IEC 15693 reading field and capable of reading a simple temperature sensor, wirelessly providing the value of that to the reader.
