2 Internal Memory in the CPU Unit
2-2
CJ2 CPU Unit Software User’s Manual
2-1 Overview
As shown in the following diagram, the internal memory in the CPU Unit consists of built-in flash mem-
ory and built-in RAM. The built-in RAM is used as execution memory and the built-in flash memory is
used as backup memory.
The built-in flash memory backs up the user program and parameters, and stores the program source,
comment, and network symbols. Data is held in this area even without depending on a battery. I/O
memory is not backed up.
The built-in RAM is the execution memory for the CPU Unit. The user program, parameters, and I/O
memory are stored in the built-in RAM, and the built-in RAM is backed up by battery.
If the battery does not work (e.g., if the battery voltage is low or no battery is installed), the I/O memory
data is lost. The user program and parameters are backed up to the built-in flash memory, so they are
not lost.
2-1-1 Memory Configuration
Built-in Flash Memory
Built-in RAM
Built-in Flash Memory
Built-in RAM
CPU Unit
User Program Area
(Backup)
Parameter Area
(Backup)
Source and
Comment Areas
Network Symbols (Tags)
Data is held in these areas
without depending on a
backup battery.
Data is backed up in these
areas by a battery.
Backup
Battery
(CJ1W-BAT01)
User Program Area
Parameter Area
I/O Memory Areas
Execution Memory
Backup Memory
Tag Memory
Automatic backup
Read at startup
Automatic backup
Read at startup
Automatic backup
Read at startup
FB Program Area
(Backup)
FB Program Area
Parameter Area
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