Data Carrier Memory Check Function - Omron V600 Series User Manual

Section 4
Function

Data Carrier Memory Check Function

A memory check can be made using the MANAGEMENT DATA CHECK/CALCULATE commands (MDC/
MDK). A CRC (Cyclic Redundancy Check) code calculation, overwrite, and comparison are made, using the
check block unit 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 MANAGE-
MENT DATA CHECK/CALCULATE (MDC/MDK).
p.116
■ Example Using MANAGEMENT DATA CHECK/CALCULATE (MDC/MDK)
In the following example, the data in addresses 0010H to 0012H is checked.
1. In this example, the following data already
exists in the memory.
0010
0011
0012
0013
0014
3. Execute MDC1001005 (CRC compared).
The normal response MD75 will be returned if
the data coincides.
0010
0011
0012
0013
0014
RFID System
68
Operation Manual
12
H
34
H
56
H
12
H
34
H
56
H
5C
H
D6
H
Address
0000
0001
Area start
address
Number of
check block bytes
CRC upper digit
CRC lower digit
2. Execute MDK1001005 (CRC calculated).
The CRC code 5CD6 calculated from the data
123456 is written to addresses 0013H and
0014H.
12
0010
H
34
0011
H
56
0012
H
0013 5C
H
D6
0014
H
If a data error occurs, MD76 (a data error
warning) will be returned.
00
0010
H
34
0011
H
0012 56
H
0013 5C
H
0014 D6
H
Check code calculation area
(Number of check block
bytes - 2)
Check code area
(2 bytes)
Data error