Essel Technology RFID A1, User Manual, Page: 37 / 60

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4.2.13 Decrement Value (0x0D)
Table 4.13
The Decrement Value command is an operation on a value-type block, as defined by the Mifare standard. It takes as
arguments the block address where the value is stored (Block Address), the signed 32-bit integer number which will
be subtracted from the value (Delta Value), the Authentication Key Number and (optionally) the Authentication Key.
The command reads the value from the block into the volatile memory on the tag and decrements it by the delta
value. There is no further operation done. To store the value in the same or another block, the user must execute
the Transfer Value command.
Command Number
Command Name
Valid Tag Types
Argument Offset [bytes]
0x00 0x01 0x05 0x06
Argument Name
Block Address Delta Value
Authentication Key
Number
Authentication Key
Argument Size [bytes] 0x01 0x04 0x01 0x06
Argument Description
Address of the block in
the memory from
which the value is to be
read and incremented.
Block has to be
formatted as a value
type block before
reading.
Signed 32-bit number
to be substracted from
the value read from the
tag block.
The 6 least significant
bits define the
Authentication Key
Number from 0 to 39
that is to be used to
read the data. If the
most significant bit (bit
7) is set, then the key
will be used as Key B. If
it is zero it will be used
as Key A. If bit 6 is set,
then the key will be
taken from the
argument list (next 6
bytes).
Optional parameter
used when bit 6 in the
preceding
Authentication Key
Number argument is
set. This key will be
used as Key B if bit 7 of
the Authentication Key
Number is set, or as
Key A if it is zero. The
byte order is the least
significant byte first.
0x0D
Decrement Value
Mifare Classic