Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 84)

Preface MicroLogix 1000 Programmable Controllers User Manual
4–8
Power Down
When a power down occurs, only the retentive data is transferred from the RAM to
the EEPROM. (The program files do not need to be saved to the EEPROM since
they cannot be modified during normal operation.) If for some reason power is lost
before all of the retentive data is saved to the EEPROM, the retentive data is lost.
This may occur due to an unexpected reset or a hardware problem.
CPU
EEPROM
Backup Data
Retentive Data
Program Files
RAM
CPU Workspace
Retentive Data
Program Files
Programming Device
Power Up
During power up, the micro controller transfers the program files from the
EEPROM to the RAM. The retentive data is also transferred to the RAM, provided
it was not lost on power down, and normal operation begins.
CPU
EEPROM
Backup Data
Retentive Data
Program Files
RAM
CPU Workspace
Retentive Data
Program Files
Programming Device