69
Data Check
Section 5-7
Note
1.
For a Data Carrier with a replaceable battery (V600-D2KR16), the battery
is checked when any address is read or written.
2.
The Data Carriers contain a lithium/thionyl chloride battery. If this battery
is not used for several months, the internal resistance in the battery will in-
crease. Because of this, the low battery check may detect a low battery for
a Data Carrier even though the battery has sufficient life remaining. This is
due to the increased internal resistance in the battery and not to the life of
the battery. When using a Data Carrier that has not been used for months
after purchase, perform read operations for about 10 minutes to activate
the battery and return the internal resistance of the battery to normal sta-
tus. This will not meaningfully affect the life of the battery.
5-7
Data Check
A check code can be attached to data in a Data Carrier to detect data errors
caused by a low battery in SRAM Data Carriers, an expired EEPROM Data
Carrier, or other factors. A CRC code generated with the polynomial X
16
+ X
12
+ X
5
+ 1 is used as the check code.
A memory check is performed by using the Data Check command with a Cal-
culation processing specification to write the check code and a Verification
processing specification to verify the check code. The start address and the
number of bytes determine the specified check block. All but the last 2 bytes
are the area to calculate and the last 2 bytes are the check code area.
When the Data Check command is executed to write the check code, the
CRC code is calculated for the area to calculate and written in the check code
area.
When the Data Check command is executed to verify the check code, the
CRC code is calculated for the area to calculate and compared with the data
in the check code area. If the calculated code is the same as the data in the
check code area, the Normal End Flag (word (n + 7), bit 01) in Unit Status will
!
WARNING
The SRAM-type Data Carrier has a built-in lithium battery which can com-
bust or explode if mishandled. Do not disassemble the Data Carrier, or sub-
ject it to high pressure or high temperatures (of 100
°
C or more), or dispose
of it by incineration.
Area start
address
CRC (upper digit)
CRC (lower digit)
Address (hex)
Check code
area (2 bytes)
Area for check
code calculation
(number of check block
bytes minus 2)
Number of
check block
bytes
00
01
Содержание CJ - 12-2004
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Страница 91: ...72 Data Check Section 5 7...
Страница 141: ...122 Sample Programming Appendix B...
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