EM4205-EM4305
co14- co17
Last Default Read Word (LWR)
Words 14 and 15: Protection Words
Bits co14 - co17 contain the binary word address of the last
word read in default read. co17 is MSB and co14 is LSB.
Please, note that the LWR valid range is from Word 5 up
to Word 13.
A mechanism is available to prevent individual EEPROM
words from being modified by the write command.
Memory locations 14 and 15 are used for this purpose
(see table 5). They form a single Protection Register. Its
content determines the write protection status of individual
EEPROM words.
co18:
Read Login
When set to logic 1, the reading of all words, except
Words 0 and 1, by using the Read Word command is
protected. Reading any of these words using the Read
Word command, can be done upon successful execution
of a Login command.
pr0 - pr13:
Protection Bits
Bits pr0 to pr13 are used to write-protect individual
EEPROM words, 0 to 13 respectively.
When set to 0, the corresponding EEPROM word can be
modified through the Write Word command.
co19:
Not used
This bit must be set to logic 0.
When set to 1, the word is write-protected and cannot be
modified.
co20:
Write Login
When the Write Login bit is set to logic 1, modification of
EEPROM content is protected. Writing any word using
Write Word command or changing protection using
Protect command, can be done upon successful
execution of a login command.
Note: Independent of write login configuration bit state, Password
(word 2) reprogramming can be done upon successful execution
of a login command.
pr 14:
Protection Bit
Bits pr14 is used to protect the Protection Register itself.
pr15:
Status Bit
Bits pr15 is an internal status bit. Given the Protection
Register implementation using two EEPROM words, pr15,
when read as 1, identifies the currently active word.
Currently active word holds the Protection Register
content while the other non-active word is erased (all 0
content).
.
co21 – co22:
Not used
These bits must be set to logic 0.
pr16 - 31:
Bits pr16 - 31 are unused.
Not used
co23:
Disable
When this bit is set to logic 1, Disable command is
accepted.
The Protection Register can only be modified through the
Protect Command (see paragraph "Protect Command").
co24:
RTF (Reader Talk First)
When the RTF bit is set to logic 1, there is no modulation
in Default Read mode, and the EM4205/4305 operates in
Reader Talk First (RTF) mode. In RTF mode, the
communication is done only using commands.
The Write Word command has no effect on the Protection
Words.
The Read Word command can be used to read the
Protection Words content.
co25:
Not used
This bit must be set to logic 0.
Note: The above implementation, using two physical words in a
read/write EEPROM to represent a single Protection Register,
was chosen as an additional security feature. This double
buffered mechanism caters to the fact an EEPROM-write
operation internally generates an erase-to-zero operation
co26:
Pigeon mode
When the Pigeon mode bit is set to logic 1, LWR definition
(co14- co17) is ignored, EM4205/4305 starts to read the 32
bits of Word 5, then reads the 16 LSB bits of Word 6 and
continue with the 16 LSB bits of Word 7.
followed
by the
actual write
operation.
Should
the operation be interrupted for any reason (e.g. tag removal from
the field) the double buffer scheme ensures that no unwanted
"0"-Protection Bits (i.e unprotected words) are introduced.
After sending us15 of Word 7, readout continues without
interruption with the first bit of Word 5.
This data structure permits the locking of48 bits of the
pigeon code and allows modification of the last 16 bits
before the race.
co27 - co31:
Reserved for future use
These bits must be set to logic 0.
7
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Copyright 2013, EM Microelectronic-Marin SA
4205-4305-DS-01.doc, Version 4.0, 22-Oct-13
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