Inovance H3U Series - Verification

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4
4 Instructions 4.11.2 Verication
The MODBUS instruction is used for the communication of Modbus-enabled slave devices (for example,
MD320, MD300, and MD280 series AC drives). In example 1, the PLC continuously reads data from
registers from head address K100 of slave 1 and stores the data in units from head address D10.
Usage:
Different from the RS instruction, multiple MODBUS instructions can be executed simultaneously in a
program.
The MODBUS instruction does not require the processes of setting M8122 to ON and resetting M8123.
4.11.2 Verication
Verication
CCD Check code
CRC CRC code calculation
LRC LRC code calculation
CCD: Check code
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Overview
When driving conditions are met, the CCD instruction calculates the checksum of the K data entries from
head address S. The summation result is stored in D, and the XOR logical operation result is stored in D+1.
CCD S D n
Check code Applicable model:
H3U
S Data source
Head address of consecutive units that store the variables
whose checksum will be calculated
16-bit instruction
(7 steps)
CCD: Continuous
execution
CCDP: Pulse
execution
D
Operation
result
Summation result stored in D; XOR logical operation result
stored in D+1
n
Checked
byte count
Number of bytes contained in checked variables
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Operands
Operand
Bit Element Word Element
System·User System·User Bit Designation Indexed Address Constant
Real
Number
S X Y M T C S SM D R T C SD KnX KnY KnM KnS KnSM
V,Z
Modication K H E
D X Y M T C S SM D R T C SD KnX KnY KnM KnS KnSM
V,Z
Modication K H E
n X Y M T C S SM D R T C SD KnX KnY KnM KnS KnSM
V,Z
Modication K H E
Note: The elements in gray background are supported.
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Function
Two types of checksum operation are performed on n variables from head address S. The summation
result is stored in D, and the XOR logical operation result is stored in D+1. The string checksum operation
ensures correct data transfer during communication.