ISO/IEC 15693

ISO 15693 is an ISO standard for "Vicinity Cards", i.e. cards which can be read from a greater distance as compared to Proximity cards.

ISO 15693 systems operate on 13.56MHz frequency, and offer maximum read distance of 1-1.5 metre. An example of this being the Radio Identification tags (RFID) used to collect toll electronically these days.

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).

Communication to the card

Communication from the reader to the card uses a Amplitude Shift Keying with 10% or 100% Modulation index.

The data coding is:

1 out of 4 pulse position modulation

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 kb/s.

Communication to the reader

The card has two ways to send its data back to the reader:

Amplitude Shift Keying

Amplitude Shift Keying 100% modulation index on a 423,75 kHz Subcarrier The data rate can be:

Low 6,62 kbits/s ( fc/2048)

High 26,48 kbits/s ( fc/512)

A logic 0 starts with 8 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 delimitors are code violations, a start of frame is:

1. an unmodulated time of 56,64 µs (768/ fc),
2. 24 pulses of 423,75 kHz
3. a logic 1

and the end of a frame is:

1. a logic 0
2. 24 pulses of 423,75 kHz
3. an unmodulated time of 56,64 µs

The data is sent using a Manchester code.

Frequency Shift Keying

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 kbits/s ( fc/2032)

High 26,69 kbits/s ( fc/508)

A logic 0 starts with 8 pulses of 423,75 kHz followed by 9 pulses of 484,28 kHz, a logic 1 is the other way round.

The data frame delimitors are code violations, a start of frame is:

1. 27 pulses of 484,28 kHz
2. 24 pulses of 423,75 kHz
3. a logic 1

and the end of a frame is:

1. a logic 0
2. 24 pulses of 423,75 kHz
3. 27 pulses of 484,28 kHz

The data is sent using a Manchester code.

External Links

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