Controller Memory Organization

Introduction

The controller memory is composed of three types of physical memory:

The Non-Volatile Memory (NVM) contains files (application, configuration files, and so on).
The Random Access Memory (RAM) is used for application execution.
The Non-Volatile Random Access Memory (NVRAM) is used to save the retain-persistent variables and diagnostic information.

Files Transfers in Memory

Item	Controller State	File Transfer Events	Connection	Description
1	–	Initiated automatically at Power ON and Reboot	Internal	Files transfer from non-volatile memory to RAM. The content of the RAM is overwritten.
1*	–	Initiated automatically at Power ON and Reboot	Internal	Operating system files transfer.
2	All states except INVALID_OS ⁽¹⁾	Initiated by user	Ethernet or USB programming port	Files can be transferred via: Web Server FTP server Controller Assistant EcoStruxure Machine Expert
3	All states	Initiated automatically by script (data transfer) or by power cycle (cloning) when an SD card is inserted	SD card	Up/download with SD card⁽¹⁾.
4	All states	Initiated by system	Internal	Save of modified retain-persistent variables and the context on power OFF.
(1) If the controller is in the INVALID_OS state, the only accessible memory is the SD card and only for firmware upgrades.

NOTE: The modification of files in non-volatile memory does not affect a running application. Any changes to files in non-volatile memory are taken into account at the next reboot, except for the user files directly used by the application.