This section describes the RAM (Random Access Memory) size for different areas of the Modicon M241 Logic Controller.
The RAM size is 64 Mbytes.
The RAM is composed of 2 areas:
dedicated application memory
OS memory
This table describes the dedicated application memory:
|
Area |
Element |
|---|---|
|
System area |
System Area Mappable Addresses %MW0...%MW59999 |
|
System and diagnostic variables (%MW60000...%MW60199) This memory is accessible through Modbus requests only. These must be read-only requests. |
|
|
Dynamic Memory Area: Read Relocation Table (%MW60200...%MW61999) This memory is accessible through Modbus requests only. These must be read-only requests. |
|
|
System and diagnostic variables (%MW62000...%MW62199) This memory is accessible through Modbus requests only. These can be read or write requests. |
|
|
Dynamic Memory Area: Write Relocation Table (%MW62200...%MW63999) This memory is accessible through Modbus requests only. These can be read or write requests. |
|
|
%MW64000…%MW65535 Reserved |
|
|
User area |
Symbols |
|
Variables |
|
|
Application |
|
|
Libraries |
To display the memory mapping in EcoStruxure Machine Expert, right-click on your controller in the Devices tree window and select Device Memory Info.
|
Variables |
Description |
|---|---|
|
PLC_R |
Structure of controller read-only system variables. |
|
PLC_W |
Structure of controller read/write system variables. |
|
ETH_R |
Structure of Ethernet read-only system variables. |
|
ETH_W |
Structure of Ethernet read/write system variables. |
|
PROFIBUS_R |
Structure of PROFIBUS DP read-only system variables. |
|
SERIAL_R |
Structure of Serial Lines read-only system variables. |
|
SERIAL_W |
Structure of Serial Lines read/write system variables. |
|
TM3_MODULE_R |
Structure of TM3 modules read-only system variables. |
For more information on system and diagnostic variables, refer to Modicon M241 Logic Controller System Functions and Variables PLCSystem Library Guide.
This table describes the memory addressing for the address sizes Double Word (%MD), Word (%MW), Byte (%MB), and Bit (%MX):
|
Double Words |
Words |
Bytes |
Bits |
||
|---|---|---|---|---|---|
|
%MD0 |
%MW0 |
%MB0 |
%MX0.7 |
... |
%MX0.0 |
|
%MB1 |
%MX1.7 |
... |
%MX1.0 |
||
|
%MW1 |
%MB2 |
%MX2.7 |
... |
%MX2.0 |
|
|
%MB3 |
%MX3.7 |
... |
%MX3.0 |
||
|
%MD1 |
%MW2 |
%MB4 |
%MX4.7 |
... |
%MX4.0 |
|
%MB5 |
%MX5.7 |
... |
%MX5.0 |
||
|
%MW3 |
%MB6 |
%MX6.7 |
... |
%MX6.0 |
|
|
%MB7 |
%MX7.7 |
... |
%MX7.0 |
||
|
%MD2 |
%MW4 |
%MB8 |
%MX8.7 |
... |
%MX8.0 |
|
... |
... |
... |
... |
||
|
... |
... |
... |
... |
... |
|
|
... |
... |
... |
... |
||
Example of overlap of memory ranges:
%MD0 contains %MB0 (...) %MB3, %MW0 contains %MB0 and %MB1, %MW1 contains %MB2 and %MB3.