User Manual

RMC70/150 and RMCTools User Manual
Command Area (RMC70)
25
D12800
-
-
Variables - Current Values (RMC150)
-
-
56-59
D28672
Variables - Initial Values (RMC150)
-
-
72-75
E0_04096
Plot Layout
31
D15872
95
E0_15872
Plot Configuration
32-39
D16384
96-103
E0_16384
Dynamic Plot Upload Area
40-47
D20480
104-111
E0_20480
Static Plot Upload Area
48-55
D24576
112-143
E0_24576
Variables - Current Values (RMC70)
56-59
D28672
-
-
Variables - Initial Values (RMC70)
64-67
E0_0000
-
-
9.3.5. Modbus Addressing
This topic describes the Modbus addressing format as used by the RMC. For other addressing
formats, see the Register Map Overview
topic.
The Modbus/RTU and Modbus/TCP address format must be used when communicating with the
RMC75S via Modbus/RTU and when communicating with the RMC75E or RMC150E
via
Modbus/TCP.
Address Format
The Modbus addressing assigns a single number to each register.
There are three different ways to refer to Modicon holding registers:
• Holding Register Address (e.g. 400059)
Holding registers are labeled with the 4 prefix to differentiate them from other types of
registers in the Modicon PLCs. Originally, they were called 40 thousand registers and
were five-digit numbers starting with a 4. However, as PLC memory grew, an extra
digit was added. So, 40059 became 400059.
• Holding Register Offset (e.g. 59)
Holding Register Offset addresses are 1-based. This is basically the Holding Register
Address stripped of the leading 4 and any leading zeros. Therefore, 400059 becomes
59. The RMC Modbus addresses are given in this format. You will need to prepend it
with a 4 and any leading zeros.
• Modbus Protocol Address (e.g. 58)
In the Modbus/RTU and Modbus/TCP protocols, the addresses are encoded using 16
bits with a number between 0 and 65,535. These are 0-based addresses. Therefore,
the Modbus protocol address is equal to the Holding Register Offset minus one. This is
mainly used internal to devices and is typically not seen by the end-user.
Determining Modbus Holding Register Offset Addresses
To obtain the Modbus holding register offset address of RMC registers, use the Register
Maps. The maps provide the Modbus offset for each register. The complete address is the
holding register offset prepended with 4 and padded with zeros if necessary. For example,
holding register offset 8193 will then become the address 408193 or 48193, depending
on the host controller.
In addition, you can use the calculation below to determine the Modbus holding register
offset, given the IEC address.
Manual Calculation
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