Addressable Flag Area (%M area)¶
Allocation of the Addressable Flag Area:
The addressable flag area for the AC500 is divided into several segments with a size of 64 kbytes per segment. A maximum of 8 segments can be addressed. The availability of the segments or partial segments depends on the CPU. The size of the %M area can be found in the technical data of the Processor ModulesProcessor Modules: Processor Modules (CPUs)
| Segment | Operands | Size, cumulative [kB] | CPU PM55x CPU PM56x | CPU PM57x | CPU PM58x | CPU PM59x |
|---|---|---|---|---|---|---|
| 0 | %MB0.0…%MB0.65535 | 64 | 2 kB | 4 kB | ||
| 1 | %MB1.0…%MB1.65535 | 128 | - | - | ||
| 2 | %MB2.0…%MB2.65535 | 192 | - | - | - | |
| 3 | %MB3.0…%MB3.65535 | 256 | - | - | - | |
| 4 | %MB4.0…%MB4.65535 | 320 | - | - | - | |
| 5 | %MB5.0…%MB5.65535 | 284 | - | - | - | |
| 6 | %MB6.0…%MB6.65535 | 448 | - | - | - | |
| 7 | %MB7.0…%MB7.65535 | 512 | - | - | - |
Note
The %M area in AC500-eCo CPUs PM55x and PM65x cannot be retained, even if declared as VAR_RETAIN. Use %R area instead of %M area if retained variables are needed.
Access to the %M Area Using the Modbus® Protocol:
The Modbus® RTU protocol is implemented in the AC500. With the help of the Modbus® protocol, the segments 0 and 1 of the addressable flag area can be accessed. The chapter Modbus Communication \ with Modbus® RTU and Modbus® TCP/IP in this documentation contains a detailed description of the Modbus® protocol and the corresponding addressing.
Note
For the AC500 CPUs PM55x and PM56x, 2kB = %MB0.0 .. %MB0.2047 (i.e., not a complete segment) are available for the addressable flag area. For the AC500 CPU PM571, 4kB = %MB0.0 .. %MB0.4095 (i.e., not a complete segment) are available for the addressable flag area. Thus, not all Modbus addresses can be accessed.
Access to Operands in the Addressable Flag Area:
The operands in the %M area can be accessed bit-wise, byte-wise, word-wise and double-word-wise.
| Byte SINT / BYTE | Byte SINT / BYTE | Word INT / WORD | Word INT / WORD |
|---|---|---|---|
| Segment 0 | |||
| %MB0.0 | %MX0.0.0 … %MX0.0.7 | %MW0.0 | %MD0.0 |
| %MB0.1 | %MX0.1.0 … %MX0.1.7 | ||
| %MB0.2 | %MX0.2.0 … %MX0.2.7 | %MW0.1 | |
| %MB0.3 | %MX0.3.0 … %MX0.3.7 | ||
| … | … | … | … |
| %MB0.65532 | %MX0.65532.0 … %MX0.65532.7 | %MW0.32766 | %MD0.16383 |
| %MB0.65533 | %MX0.65533.0 … %MX0.65533.7 | ||
| %MB0.65534 | %MX0.65534.0 … %MX0.65534.7 | %MW0.32767 | |
| %MB0.65535 | %MX0.65535.0 … %MX0.65535.7 | ||
| Segment 1 | |||
| %MB1.0 | %MX1.0.0 … %MX1.0.7 | %MW1.0 | %MD1.0 |
| %MB1.1 | %MX1.1.0 … %MX1.1.7 | ||
| %MB1.2 | %MX1.2.0 … %MX1.2.7 | %MW1.1 | |
| %MB1.3 | %MX1.3.0 … %MX1.3.7 | ||
| … | … | … | … |
| %MB1.65532 | %MX1.65532.0 … %MX1.65532.7 | %MW1.32766 | %MD1.16383 |
| %MB1.65533 | %MX1.65533.0 … %MX1.65533.7 | ||
| %MB1.65534 | %MX1.65534.0 … %MX1.65534.7 | %MW1.32767 | |
| %MB1.65535 | %MX1.65535.0 … %MX1.65535.7 | ||
| Segment 2 | |||
| %MB2.0 | %MX2.0.0 … %MX2.0.7 | %MW2.0 | %MD2.0 |
| %MB2.1 | %MX2.1.0 … %MX2.1.7 | ||
| %MB2.2 | %MX2.2.0 … %MX2.2.7 | %MW2.1 | |
| %MB2.3 | %MX2.3.0 … %MX2.3.7 | ||
| … | … | … | … |
| %MB2.65532 | %MX2.65532.0 … %MX2.65532.7 | %MW2.32766 | %MD2.16383 |
| %MB2.65533 | %MX2.65533.0 … %MX2.65533.7 | ||
| %MB2.65534 | %MX2.65534.0 … %MX2.65534.7 | %MW2.32767 | |
| %MB2.65535 | %MX2.65535.0 … %MX2.65535.7 | ||
| … | … | … | … |
| Segment 7 | |||
| %MB7.0 | %MX7.0.0 … %MX7.0.7 | %MW7.0 | %MD7.0 |
| %MB7.1 | %MX7.1.0 … %MX7.1.7 | ||
| %MB7.2 | %MX7.2.0 … %MX7.2.7 | %MW7.1 | |
| %MB7.3 | %MX7.3.0 … %MX7.3.7 | ||
| … | … | … | … |
| %MB7.65532 | %MX7.65532.0 … %MX7.65532.7 | %MW7.32766 | %MD7.16383 |
| %MB7.65533 | %MX7.65533.0 … %MX7.65533.7 | ||
| %MB7.65534 | %MX7.65534.0 … %MX7.65534.7 | %MW7.32767 | |
| %MB7.65535 | %MX7.65535.0 … %MX7.65535.7 | ||