Mitsubishi Electric MELSEC-Q/L - CRC Operation

7 APPLICATION INSTRUCTIONS
7.5 Data Processing Instructions
455
7
CRC operation
CRC(P)
Processing details
• Generates the CRC value of n points of 8-bit data (byte units) starting from the device specified by (S) and stores it in the
device specified by (D). "X
16
+X
15
+X
2
+1" is used as the generator polynomial to generate the CRC value. These
instructions support two modes, 16-bit conversion mode and 8-bit conversion mode, used for calculation of the CRC value.
The two conversion modes can be selected by SM772 ON/OFF. The operation in each conversion mode is described
below.
■16-bit conversion mode (when SM772 is OFF)
CRC operation is performed for the upper 8 bits (byte units) and lower 8 bits (byte units) in the device specified by (S). The
operation result is stored in the 16 bits of one point of the device specified by (D). The CRC value when n = 6 is shown below.
In 16-bit conversion mode, the 6 bytes at the shaded positions in the following figure are the operation target. Here, the CRC
value is "A57BH" and accordingly "A57BH" is stored in the device specified by (D).
• QnUDVCPU, LCPU: The serial number (first five digits) is "16112" or later.
(S): Start number of the devices where the target data of CRC value generation is stored (BIN 16 bits)
(D): Number of the device where the CRC value generated is stored (BIN 16 bits)
n: Number of 8-bit data blocks for which the CRC value is to be determined or the number for the device where the number of 8-bit data blocks is stored
(setting range: 1 to 256) (BIN 16 bits)
Setting
data
Internal device R, ZR J\ U\G Zn Constant
K, H
Others
Bit Word Bit Word
(S) 
(D) 
n 
Basic
High
performance
Process Redundant Universal
Ver.
LCPU
Ver.
CRC
CRCP
n
n
S D
S D
CRC
CRCP
Command
Command
Device Decimal
Hexadecimal
Upper bits Lower bits
61
H 64H
10H 7BH
FAH CBH
FFH FFH
7FH F9H
27H 10H
D0 24932
D1 4219
D2 -1333
D3 -1
D4 32761
D5 10000