Read With Error Correction - Mitsubishi MELSEC-Q EQ-V680D1 User Manual

6. HOW TO COMMUNICATE WITH ID TAGS

6.2.11 Read with error correction

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The Read with Error Correction command reads from the ID tag the number of byte sets
specified in the number of processed points specification area (Un\G4, Un\G4004) +
the check code (five bytes) from the address specified in the head address specification
area (Un\G3, Un\G4003), and checks the correctness of the data from the check code.
When a 1-bit memory error is corrected, the data correction flag (bit 3) of the error
details storage area (Un\G41, Un\G4041) turns ON and error detection (X5, XD) turns
ON. The normal data after error correction are stored in the data storage area
(Un\G100 to UN\G1123, UN\G4100 to Un\G5123).
For details of the error correction function, refer Section 5.6, "ID Tag Memory Error
Correction Function".
(1) Example of use
(a) When executing the Read with Error Correction command in the data storage
order 0000
(upper -> lower), for the four bytes from address 0010
H
ID tag
Address
Before
b7
execution
0010 12
H H
34
0011
H
H
56
0012
H
H
78
0013
H
H
F0
0014
H H
67
0015
H
H
0016 00
H H
0C
0017
H
H
0F
0018
H
H
A : No. of read bytes (4 bytes)
B : Memory check code (2 bytes)
C : Error correction code (3 bytes)
(b) When executing the Read with Error Correction command in the data storage
order 0000 (upper -> lower) for the four bytes from address 0010
H
memory error is corrected
ID tag
Address
Before
b7
execution
02
0010
H
H
34
0011
H
H
0012 56
H H
78
0013
H
H
F0
0014
H
H
67
0015
H
H
0016 00
H H
0C
0017
H
H
0F
0018
H
H
b15
Un\G100
Un\G101
A
B
C
b15
Un\G100
Un\G101
1-bit memory
Executing the
error
Read with Error
Buffer memory
After
b0
execution
12 34
H
56 78
H
Buffer memory
After
b0
execution
12 34
H
56 78
H
.
H
and a 1-bit
H
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