EM4450
EM4550
Timing Characteristics
VDD =2.5V, VSS=0V , fcoil = 125 kHz Sine wave, Vcoil = 1Vpp
,
Top = 25°C
unless otherwise specified
All timings are derived from the field frequency and are specified as a number of RF periods..
Parameter
Symbol
Opt64
trdb
Conditions
including LIW
VDD = 3V
Value
Unit
Option : 64 clocks per bit
Read Bit Period
64
320
3200
64
RF periods
RF periods
RF periods
RF periods
RF periods
RF periods
RF periods
LIW/ACK/NACK pattern duration
Read 1 Word Duration
Processing Pause Time
Write Access Time
tpatt
trdw
tpp
twa
64
Initialization Time
tinit
2112
3200
EEPROM write time
Option : 32 clocks per bit
Read Bit Period
twee
Opt32
trdb
32
160
1600
32
RF periods
RF periods
RF periods
RF periods
RF periods
RF periods
RF periods
LIW/ACK/NACK pattern duration
Read 1 Word Duration
Processing Pause Time
Write Access Time
tpatt
trdw
including LIW
VDD = 3V
tpp
twa
32
Initialization Time
tinit
1056
2624
EEPROM write time
twee
RF periods represent periods of the carrier frequency emitted by the transceiver unit. For example, if 125 kHz is used :
The Read bit period (Opt64) would be : 1/125'000*64 = 512 µs, and the time to read 1 word : 1/125'000*3200 = 25.6 ms.
The Read bit period (Opt32) would be : 1/125'000*32 = 256 µs, and the time to read 1 word : 1/125'000*1600 = 12.8 ms.
ATTENTION
Due to amplitude modulation of the coil-signal, the clock-extractor may miss clocks or add spurious clocks close
to the edges of the RF-envelope. This desynchronisation will not be larger than ±3 clocks per bit and must be
taken into account when developing reader software.
Functional Description
General
The EM4450/4550 is supplied by means of an electromagnetic field induced on the attached coil. The AC voltage is rectified
in order to provide a DC internal supply voltage. When the DC voltage crosses the Power-On level, the chip enters the
Standard Read Mode and sends data continuously. The data to be sent in this mode is user defined by storing the first and
last addresses to be output. When the last address is sent, the chip will continue with the first address until the transceiver
sends a request. In the read mode, a Listen Window (LIW) is generated before each word. During this time, the
EM4450/4550 will turn to the Receive Mode (RM) if it receives a valid RM pattern. The chip then expects a valid command.
Mode of Operation
Pow er-On
Init
Get Command
Standard
Read Mode
Execute Command
Login
Receive
Mode
NO
YES
Write Word
Write Password
Selective Read
Reset
request ?
Send w ord
Fig. 4
4
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