Omron V600 Series User Manual page 68

Section 4
Function
Data Carriers without Batteries
MANAGEMENT DATA SUBTRACTION/LIMIT commands (MDS/MDL) can be used to determine whether
the overwrite count for the EEPROM Data Carrier has been exceeded. By executing the MANAGEMENT
DATA SUBTRACTION command (MDS), the number of overwrites is decremented from the data in the
specified overwrite count control area, and whether the data has exceeded the limit is determined.
By executing the MANAGEMENT DATA LIMIT command (MDL), the number of overwrites is written to
the data in the specified overwrite count control area, and whether the data has exceeded 100,000 writes
is determined.
The MANAGEMENT DATA LIMIT command (MDL) is designed for Data Carriers without Batteries that
have an expected life specification of 100,000 writes.
■ MDS Command
The overwrite count control area consists of 3 bytes from the
start address. The decremented value of the overwrite count
is written in this area, and if this value is 0 (00H) an end code
of 76 will be returned as a warning. Therefore, to enable con-
trol of the number of overwrites, the maximum number of over-
writes must be written to the overwrite count control area
beforehand. The user-specified number of overwrites can be
set to up to 16,700,000. The number of overwrites in the spec-
ifications for Data Carriers without batteries, however, is 300,000 overwrites (0493E0H) at 40C max., so be sure
to set the number of overwrites to 300,000 or lower.
The number of overwrites is controlled using hexadecimal values.
The current value can be read using the READ command.
If the control area data is already 0, the control area value will not be refreshed, and only a warning will be
returned as a response.
When the refresh count is set as 00H, the count will not be updated, and only an overwrite count check will be per-
formed.
Set the start address to between @@@0H and @@@5H or between @@@8H and @@@DH. If the start address is set
between @@@6H and @@@7H or between @@@EH and @@@FH, an address error (error code: 7A hexadecimal) will
be returned as the end code.
For details on command format, refer to MANAGEMENT DATA SUBTRACTION/LIMIT (MDS/MDL).
■
Application Example for MANAGEMENT DATA SUBTRACTION (MDS)
Using the Three Bytes from Address 0010H as the Overwrite Count Area
1. An overwrite count initial value of 100,000
times is written in the control area.
"WTH100100186A0"
3. The accumulated count is 100,000 times.
When "MDS1001000" is executed, "MD76"
will be returned (overwrite count exceeded).
RFID System
66
Operation Manual
p.118
01
0010 H
86
0011 H
A0
0012
H
00
0010 H
00
0011
H
00
0012
H
(V600-D23P@@)
Area start address
2. Enter an overwrite count of 5. "MDS1001005"
A total of 5 times will be decremented from
100,000.
0010
0011
0012
Upper digit
Middle digit
3 bytes
Lower digit
01
H
86
H
9B
H