125
RFID System
User’s Manual
Section 4
Memor
y
Ch
eck
F
unct
ion in
RF Ta
g
Section 4
Functions
Memory Check Function in RF Tag
A memory check can be made using the DATA CHECK command (MD C/K). A CRC (Cyclic Redundancy
Check) code calculation, overwrite, and comparison are made, using the check block units specified by the
user. The CRC code is calculated from the generated polynomial expression x
16
+ x
12
+ x
5
+ 1.
The calculation area is the portion of the check block
specified by the start address and the number of bytes
excluding the last two bytes. The last two bytes are the
check code area. When check code write is specified
(transaction code: K), the CRC of the calculation area
data is calculated and written to the check code area.
When data comparison is specified (transaction code:
C), the CRC of the calculation area data is calculated
and a comparison made with the check code area
data. If they coincide, end code 00 is returned,
indicating normal transmission, and if they do not
coincide, end code 76 is returned as a warning.
For details on the command format, refer to
(MD C/K)
.
Example Using the RF Tag's DATA CHECK Command
In the following example, the data in address 0010 to 0012 (hex) is checked
1. In this example, the following data already
exists in the memory.
2. Execute MDSTK1001005
(calculation transaction).
The CRC code 5CD6 calculated from the data
123456 is written to addresses 0013H and
0014H.
3. Execute MDSTC1001005
(comparison transaction).
The normal response MD0010 will be
returned if the data coincides.
If the data error occurs, MD7610 (a data error
warning) will be returned.
0000
0001
Area start
address
Number of check
block bytes
Check code area
(2 bytes)
Address (hex)
CRC (upper digit)
CRC (lower digit)
(Number of check
block bytes
−
2)
Check code
calculation area
0010
0011
0012
0013
0014
34 hex
12 hex
56 hex
0010
0011
0012
0013
0014
34 hex
12 hex
56 hex
5C hex
D6 hex
34 hex
12 hex
56 hex
5C hex
D6 hex
0010
0011
0012
0013
0014
0010
0011
0012
0013
0014
34 hex
00 hex
56 hex
5C hex
D6 hex
Data error
