6

T5557

4517E–RFID–02/03

Any field gap occurring during this initialization phase will restart the complete

sequence. After this initialization time the T5557 enters regular-read mode and modula-

tion starts automatically using the parameters defined in the configuration register.

Tag to Reader

Communication

During normal operation, the data stored within the EEPROM is cycled and the Coil 1,

Coil 2 terminals are load modulated. This resistive load modulation can be detected at

the reader module.

Regular-read Mode

In regular-read mode data from the memory is transmitted serially, starting with block 1,

bit 1, up to the last block (e.g., 7), bit 32. The last block which will be read is defined by

the mode parameter field MAXBLK in EEPROM block 0. When the data block

addressed by MAXBLK has been read, data transmission restarts with block 1, bit 1.

The user may limit the cyclic datastream in regular-read mode by setting the MAXBLK

between 0 and 7 (representing each of the 8 data blocks). If set to 7, blocks 1 through 7

can be read. If set to 1, only block 1 is transmitted continously. If set to 0, the contents of

the configuration block (normally not transmitted) can be read. In the case of MAXBLK =

0 or 1, regular-read mode can not be distinguished from block-read mode.

Figure 6. Examples for Different MAXBLK Settings

Every time the T5557 enters regular- or block-read mode, the first bit transmitted is a

logical ‘0’. The data stream starts with block 1, bit 1, continues through MAXBLK, bit 32,

and cycles continuously if in regular-read mode .

Note:

This behavior is different from the original e555x and helps to decode PSK-modulated

data.

Block-read Mode

With the direct access command, the addressed block is repetitively read only. This

mode is called block-read mode. Direct access is entered by transmitting the page

access opcode (‘10’ or ‘11’), a single ‘0’ bit and the requested 3-bit block address when

the tag is in normal mode.

In password mode (PWD bit set), the direct access to a single block needs the valid

32-bit password to be transmitted after the page access opcode whereas a ‘0’ bit and

the 3-bit block address follow afterwards. In case the transmitted password does not

match with the contents of block 7, the T5557 tag returns to the regular-read mode.

Note:

A direct access to block 0 of page 1 will read the configuration data of block 0, page 0.

A direct access to bock 3 .. 7 of page 1 reads all data bits as zero.

e5550 Sequence

Terminator

The sequence terminator ST is a special damping pattern which is inserted before the

first block and may be used to synchronize the reader. This e5550-compatible sequence

terminator consists of 4 bit periods with underlaying data values of ‘1’. During the sec-

ond and the fourth bit period, modulation is switched off (Manchester encoding –

switched on). Biphase modulated data blocks need fixed leading and trailing bits in com-

bination with the sequence terminator to be identified reliable.

Block 1

Block 4

Block 5

Block 1

Block 2

MAXBLK = 5

MAXBLK = 2

MAXBLK = 0

Block 1

Block 2

Block 1

Block 2

Block 1

Block 0

Block 0

Block 0

Block 0

Block 0

0

0

0

Loading block 0

Loading block 0

Loading block 0