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4-5 Memory Check Function
By adding a check code to a data in a tag, you can detect a data error arisen from memory rewrite life or unintentional factor. A CRC
code of generating polynomial X
For memory check, a memory check command (MC) to write a check code and a memory calculation command (MK) to verify the
check code are used.
In a check block specified by the first address and the number of
bytes, an area excluding the last 2 bytes of the block is a target area
to be calculated and the last 2 bytes are a check code area.
When a command to write the check code is sent, the CRC code of
data in the target area for calculation is calculated and it is written
into the check code area. When a data verification command is
sent, the CRC code of data in the target area for calculation is cal-
culated and it is compared with data of the check code area. If
those data match, "0" is returned. This shows that the data is cor-
rect in a response status flag. If those data do not match, "1" is
returned as warning.
<How to use>
Calculate/write the check code with the memory check command (MC) after writing a data and verify the check code with the memory
calculation command (MK) before reading it. Beforehand, you can detect data corruption in the tag which is not accessed.
Writing stage
Data writing
Check code calculation
Check code verification
Reading stage
Data reading
4-10
16
12
5
+ X
+ X
+ 1 is used as the check code.
Address
First address in this
area
→
(High order
digit)
(Low order
digit)
Target area for check code
calculation
(Number of check block
bytes: 2)
Check code area (2 bytes)
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