EM4450
EM4550
After reception of the command, the address, and the data, the EM4450/4550 will check the parity, the write protection
status, the Login status, and also if the available power from the RF field is sufficient. If all the conditions are satisfied, an
acknowledge pattern (ACK) will be issued afterward and the EEPROM writing process will start. At the end of programming,
the chip will send an Acknowledge pattern (ACK). If at least one of the checks fails, the chip will issue a no acknowledge
pattern (NAK) instead of ACK and return to the Standard Read Mode. The Transceiver will keep the RF field permanently
"ON" during the whole writing process time.
The Read After Write function (bit 17 of Control word) controls the mode of operation following a write operation. When
"ON" the latest written word will be read out and output next to the ACK pattern and two Listen Windows (LIW-LIW) even if
the word is read protected. When "OFF", the ACK is followed immediately by a LIW-LIW and FWR. The last written word is
not output.
If a request from the transceiver to return in receive mode (RM) is generated during the LIW, another word can be written in.
Otherwise, the EM4450/4550 will return in the Standard Read Mode.
Write 1 word
twa
twee
output
input
WORD n LIW
RM WRITE WORD ADDRESS DATA
ACK
ACK LIW LIW
FWR
TRANSCEIVER RF FIELD "ON"
Write severalwords
twa
twee
output
input
WORD n LIW
RM WRITE WORD ADDRESS DATA
ACK
ACK LIW
RM WRITE WORD ADDRESS DATA
TRANSCEIVER RF FIELD "ON"
Read After Write function
twa
twee
output
input
WORD n LIW
RM WRITE WORD ADDRESS DATA
ACK
ACK LIW LIW Last Written LIW LIW FWR
TRANSCEIVER RF FIELD "ON"
Write not allowed or wrong transmission
twa
output
input
WORD n LIW
RM WRITE WORD ADDRESS DATA
NACK LIW LIW
FWR
TRANSCEIVER RF FIELD "ON"
Fig. 16
9
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