AutomationDirect Technical Support

AutomationDirect | Direct Sales in US and Canada | 1-800-633-0405

DL-340 CPU Modbus® Address Cross-Reference Table

340 Data Type	Octal Range 340 Ref (Oct)	Modbus Data Type	Modbus Addr. (Hex)	Modbus Addr. (Dec)	Func. Code
Physical IO	0 - 167	INPUT and COIL	0000-0077	0 - 119	1,2,5,15
Control Relays	170 - 377		0078-00FF	120 - 255
Shift Register Bits	400 - 577		0100-017F	256 - 383
Timer/Counter Status	600 - 677		0180-01BF	384 - 447
Physical IO	700 - 777		01C0-01FF	448 - 511
Control Relays	1000 - 1077		0200-023F	512 - 575

User Registers	400 - 577	INPUT and HOLDING Registers	0040-007F	64 - 127	3,4,6,16
Timer/Counter Acc.	600 - 677		0000-003F	0 - 63
User Registers	700 - 777		0080-00BF	128 - 191

NOTES:

R400 - R577 and R700 - R777 are 8 bit registers in the 340 CPU. When requesting these registers via Modbus, two registers are returned for each item requested. The order of the registers is byte-swapped, i.e. if 1 item starting at register R400 is requested the information will come back as (R401, R400).

To calculate the starting Modbus address of a register you will have to use the following formula:

    RegAddr   = Desired Register Address
    BaseReg   = Base Register Address (either 400 or 700)
    DecOffset = Base of Modbus Address in Decimal (either 64 or 128)
    HexOffset = Base of Modbus Address in Hex (either 0x40 or 0x80)
    for Decimal
        ModbusAddr = OctToDec((RegAddr - BaseReg) / 2) + DecOffset
    for Hex
        ModbusAddr = OctToHex((RegAddr - BaseReg) / 2) + Hex Offset

The status of some of the addresses shown here are controlled by the CPU, by the placement of modules in the base, or by the RLL program. Modbus communications will not overwrite these addresses.

MODBUS is a registered trademark of Modicon, Inc.