Automationdirect.com DL06, User Manual

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DL06 Micro PLC User Manual; 3rd Edition Rev. E
4–15
Chapter 4: System Design and Configuration
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If Your MODBUS Host Software Requires an Address ONLY
Some host software does not allow you to specify the MODBUS data type and address. Instead,
you specify an address only. This method requires another step to determine the address, but
it’s still fairly simple. Basically, MODBUS also separates the data types by address ranges as
well. So this means an address alone can actually describe the type of data and location. This
is often referred to as “adding the offset”. One important thing to remember here is that two
different addressing modes may be available in your host software package. These are:
• 484 Mode
• 584/984 Mode
We recommend that you use the 584/984 addressing mode if your host software allows you
to choose. This is because the 584/984 mode allows access to a higher number of memory
locations within each data type. If your software only supports 484 mode, then there may be
some PLC memory locations that will be unavailable. The actual equation used to calculate the
address depends on the type of PLC data you are using. The PLC memory types are split into
two categories for this purpose.
• Discrete – X, SP, Y, CR, S, T (contacts), C (contacts)
• Word – V, Timer current value, Counter current value
In either case, you basically convert the PLC octal address to decimal and add the appropriate
MODBUS addresses (as required). The table below shows the exact equation used for each
group of data.
Discrete Data Types
DL06 Memory Type
PLC Range
(Octal)
Address
(484 Mode)
Address
(584/984 Mode)
MODBUS Data
Type
Global Inputs (GX)
GX0-GX1746 1001 - 1999 10001 - 10999 Input
GX1747-GX3777 – 11000 - 12048 –
Inputs (X)
X0 – X777 – 12049 - 12304 Input
Special Relays (SP)
SP0 – SP777 – 13073 - 13584 Input
Global Outputs (GY)
GY0 - GX3777 1 - 2048 1 - 2048 –
Outputs (Y)
Y0 – Y777 2049 - 2560 2049 - 2560 Output
Control Relays (CR)
C0 – C1777 3073 - 4096 3073 - 3584 Output
Timer Contacts (T)
T0 – T377 6145 - 6400 6145 - 6400 Output
Counter Contacts (CT)
CT0 – CT177 6401 - 6656 6401 - 6656 Output
Stage Status Bits (S)
S0 – S1777 5121 - 6144 5121 - 6144 Output