MODBUS Address Table¶
A range of 128 kbytes is allowed for the access via MODBUS, i.e., the segments line 0 and line 1 of the addressable flag area (%M area) can be accessed. Thus, the complete address range 0000hex up to FFFFhex is available for MODBUS.
The availability of the segments depends on the CPU. The size of the %M area can be found in the technical data of the CPUs and in the target system settings.
Inputs and outputs cannot be directly accessed using MODBUS.
Address assignment (bit accesses)
The address assignment for bit accesses is done according to the following table:
| MODBUS address | Byte BYTE |
Bit (byte-oriented) BOOL |
Word WORD |
Double word DWORD |
|
|---|---|---|---|---|---|
| HEX | DEC | ||||
| Line 0 | |||||
| 0000 | 0 | %MB0.0 | %MX0.0.0 | %MW0.0 | %MD0.0 |
| 0001 | 1 | %MX0.0.1 | |||
| 0002 | 2 | %MX0.0.2 | |||
| 0003 | 3 | %MX0.0.3 | |||
| 0004 | 4 | %MX0.0.4 | |||
| 0005 | 5 | %MX0.0.5 | |||
| 0006 | 6 | %MX0.0.6 | |||
| 0007 | 7 | %MX0.0.7 | |||
| 0008 | 8 | %MB0.1 | %MX0.1.0 | ||
| 0009 | 9 | %MX0.1.1 | |||
| 000A | 10 | %MX0.1.2 | |||
| 000B | 11 | %MX0.1.3 | |||
| 000C | 12 | %MX0.1.4 | |||
| 000D | 13 | %MX0.1.5 | |||
| 000E | 14 | %MX0.1.6 | |||
| 000F | 15 | %MX0.1.7 | |||
| 0010 | 16 | %MB0.2 | %MX0.2.0 | %MW0.1 | |
| 0011 | 17 | %MX0.2.1 | |||
| 0012 | 18 | %MX0.2.2 | |||
| 0013 | 19 | %MX0.2.3 | |||
| 0014 | 20 | %MX0.2.4 | |||
| 0015 | 21 | %MX0.2.5 | |||
| 0016 | 22 | %MX0.2.6 | |||
| 0017 | 23 | %MX0.2.7 | |||
| 0018 | 24 | %MB0.3 | %MX0.3.0 | ||
| 0019 | 25 | %MX0.3.1 | |||
| 001A | 26 | %MX0.3.2 | |||
| 001B | 27 | %MX0.3.3 | |||
| 001C | 28 | %MX0.3.4 | |||
| 001D | 29 | %MX0.3.5 | |||
| 001E | 30 | %MX0.3.6 | |||
| 001F | 31 | %MX0.3.7 | |||
| 0020 | 32 | %MB0.4 | %MX0.4.0 | %MW0.2 | %MD0.1 |
| 0021 | 33 | %MX0.4.1 | |||
| 0022 | 34 | %MX0.4.2 | |||
| … | … | … | … | … | … |
| 0FFF | 4095 | %MB0.511 | %MX0.511.7 | %MW0.255 | %MD0.127 |
| 1000 | 4096 | %MB0.512 | %MX0.512.0 | %MW0.256 | %MD0.128 |
| … | … | … | … | … | … |
| 7FFF | 32767 | %MB0.4095 | %MX0.4095.7 | %MW0.2047 | %MD0.1023 |
| 8000 | 32768 | %MB0.4096 | %MX0.4096.0 | %MW0.2048 | %MD0.1024 |
| … | … | … | … | … | … |
| FFFF | 65535 | %MB0.8191 | %MX0.8191.7 | %MW0.4095 | %MD0.2047 |
Calculation of the bit variable from the \ hexadecimal address:
| Formula: | |||
|---|---|---|---|
| Bit variable (BOOL) := %MX0.BYTE.BIT | |||
| where: | DEC | Decimal address | |
| BYTE | DEC / 8 | ||
| BIT | DEC mod 8 | (Modulo division) | |
Examples:
Address hexadecimal = 16#2002
DEC := 8194
BYTE := 8194 / 8 := 1024
BIT := 8194 mod 8 := 2
Bit variable: %MX0.1024.2
Address hexadecimal = 16#3016
DEC := 12310
BYTE := 12310 / 8 := 1538,75 -> 1538
BIT := 12310 mod 8 := 6
Bit variable: %MX0.1538.6
Address hexadecimal = 16#55AA
DEC := 21930
BYTE := 21930 / 8 := 2741,25 -> 2741
BIT := 21930 mod 8 := 2
Bit variable: %MX0.2741.2
Calculation of the hexadecimal address from the bit variable:
Examples:
Bit variable := %MX0.515.4
DEC := 515 * 8 + 4 := 4124
Address hex := 16#101C
Bit variable := %MX0.3.3
DEC := 3 * 8 + 3 := 27
Address hex := 16#001B
Bit variable := %MX0.6666.2
DEC := 6666 * 8 + 2 := 53330
Address hex := 16#D052