7

T5557

4517E–RFID–02/03

The sequence terminator may be individually enabled by setting of mode bit 29

(ST = ‘1’) in the e5550-compatibility mode (X-mode = ‘0’).

In the regular-read mode, the sequence terminator is inserted at the start of each

MAXBLK-limited read data stream.

In block-read mode – after any block-write or direct access command – or if MAXBLK

was set to 0 or 1, the sequence terminator is inserted before the transmission of the

selected block.

Especially this behavior is different to former e5550 – compatible ICs (T5551, T5554).

Figure 7. Read Data Stream with Sequence Terminator

Figure 8. e5550-compatible Sequence Terminator Waveforms

Reader to Tag

Communication

Data is written to the tag by interrupting the RF field with short field gaps (on-off keying)

in accordance with the e5550 write method. The time between two gaps encodes the

‘0/1’ information to be transmitted (pulse interval encoding). The duration of the gaps is

usually 50 µs to 150 µs. The time between two gaps is nominally 24 field clocks for a ‘0’

and 54 field clocks for a ‘1’. When there is no gap for more than 64 field clocks after a

previous gap, the T5557 exits the write mode. The tag starts with the command execu-

tion if the correct number of bits were received. If there is a failure detected the T5557

does not continue and will enter regular-read mode.

Start Gap

The initial gap is referred to as the start gap. This triggers the reader to tag communica-

tion. During this mode of operation, the receive damping is permanently enabled to ease

gap detection. The start gap may need to be longer than subsequent gaps in order to be

detected reliably.

Block 1

Block 2

MAXBLK

Block 1

Block 2

Block 1

Block 2

MAXBLK

Block 1

Block 2

No terminator

ST = on

Sequence terminator

Sequence terminator

Regular read mode

Last bit

First Bit

Manchester

Bit period

Modulation

off (on)

Data '1'

Data '1'

Modulation

off (on)

bit '1' or '0'

FSK

Sequence

Waveforms per different modulation types

PP

Data '1'

Data '1'

Sequence terminator not suitable for Biphase or PSK modulation