Mitsubishi Electric MELSEC iQ-R Series - Page 947

7 APPLICATION INSTRUCTIONS
7.20 Data Processing Instructions
945
7
Processing details
• These instructions generate the CRC value for (n) 8-bit data (unit: byte) starting from the device specified by (s), and store
the CRC value to the device specified by (d). "X
16
+ X
15
+ X
2
+1" is used in the generator polynomial of the CRC value
(CRC-16). The 16-bit conversion mode and 8-bit conversion mode are available for these instructions. The conversion
mode can be selected by turning on or off SM772.
• If the value specified in (n) is 0, no processing is performed.
• These instructions calculate the CRC (cyclic redundancy check) value which is an error check method used in
communication. In addition to CRC, there are other methods to check an error, such as parity check and sum check
(checksum). For obtaining the horizontal parity value and sum check value, the CCD(P) instruction is available. ( Page
903 CCD(P))
• The operation in each conversion mode is described below.
■16-bit conversion mode (while SM772 is OFF)
In this mode, the CRC operation is executed for upper 8 bits (in units of byte) and lower 8 bits (in units of byte) of the device
specified by (s). The operation result is stored to 16 bits in one device specified in (d).
Ex.
When (n)=6
In 16-bit conversion mode, the six bytes in the following shaded portion become an operation target. The CRC value is
determined as "A57BH", and therefore "A57BH" is stored in the device specified by (d).
■8-bit conversion mode (while SM772 is ON)
CRC operation is executed only for lower 8 bits (lower byte) of the device specified by (s). With regard to the operation result,
lower 8 bits (in units of byte) are stored to the device specified by (d), and upper 8 bits (in units of byte) are stored to a device
specified by (d)+1.
Ex.
When (n)=6
In 8-bit conversion mode, the six bytes in the following shaded portion become an operation target. The CRC value is
"BDA1H" and therefore "A1H" is stored in the device specified by (d) and "BDH" is stored in the device specified by (d)+1.
Operation error
Error code
(SD0)
Description
3405H A digit other than 4 is specified in the digit-specified bit device in (s) and (d).
FFH FFH
7FH F9H
D0 24932
D1 4219
D2 -1333
D3 -1
D4 32761
27H 10HD5 10000
61H61H 64H64H
10H10H 7BH7BH
FAHFAH CBHCBH
61H 64H
10H 7BH
FAH CBH
Upper Lower
Decimal Hexadecimal
61H 64H64H
10H 7BH7BH
FAH CBHCBH
FFH FFHFFH
7FH F9HF9H
D0 24932
D1
4219
D2 -1333
D3 -1
D4 32761
27H 10H10H
64H
7BH
CBH
FFH
F9H
10HD5
10000
Upper Lower
Decimal Hexadecimal