EM4069

EM4169

Copyright

 2003, EM Microelectronic-Marin SA

10

www.emmicroelectronic.com

Modulation of Magnetic Field

The modulation envelope of the magnetic field induced by the reader is observed by the EM4069 as shown in the following

figure.

Synchronization pattern

SB

B0

B1

B2

B3

B4

B5

B6

B7

Fig. 12

Comment to above timings:

periods is suggested.

periods) Please note that during this time the Modulator load is permanently on so this is the worst case for Power Supply

level. So using shorter times than upper limit is advised. Duration of 3 bit periods is suggested.

Refer to table 4 for timings range.

In the above example, the Read ROM command (1010 0101) is sent.

After successful 8-bit command detection, the EM4069 will output continuously the ROM contents

.

Reset, Read ROM and Read Configuration Word

commands

After detecting these commands the IC returns in read

mode and starts reading corresponding block (EEPROM or

ROM).

Write Word and Write Configuration Word

commands

For Write commands, a total of 32 significant bits have to

be transferred from reader to EM4069. The 32 bits are

transferred in a sequence of 4 bytes. Each byte is headed

with start bit at logic 0 (as in normal 8-bit command) and

trailed with stop bit at logic 1. The antenna sends an

uninterrupted sequence of 40 bits (32 command bits, 4

start bits and 4 stop bits).

This data organization ensures re-synchronization of the

EM4069 with the reader signal, and avoids that wrong data

would be extracted due to missing or spurious clocks from

the clock-extractor of the IC.

The IC treats the Write command as follows:

First byte received is treated in the same way as for an 8-

bit command. In the case that the processing of the first

byte detects a Write Word command, it first puts the

modulator load OFF for 1/2 bit period. During this time, the

antenna field is High (as stop bit is at logic one) so the

internal power supply capacitor can be charged. Next the

EM4069 transitions to Start Bit Detection State with

modulator load ON and waits for start bit at logic 0. The

bit is detected, the IC then returns to the read mode.

EM4069 then continues to process the next byte.

After the fourth byte has been detected, the EM4069

verifies if the CRC check is OK and if the word, which is

addressed for writing, is not protected by the configuration

word. Next, power check is performed to determine

whether there is enough power available to write

EEPROM. This operation lasts 1.5-bit periods. In the case

all conditions above are fulfilled (CRC, protection, power

check) EEPROM is written. If one of the conditions fails,

the EM4069 returns in read mode without writing

EEPROM.