S7-300 CPU has three basic storage, including:
(1) the system store
Types of RAM used to store operational data (I/O, memory, timer, counter, etc).
(2) Mount Store
CPU module is part of the physical RAM, plus a built-in EEPROM or optional removable EEPROM cards, used to store user programs.
(3) the work store
Consume CPU module part of the physical RAM, its memory contents of CPU run time, performed by the user program unit (logic and data blocks) a copy.
CPU work store also offers block l stack (temporary local data store). • Data on the stack when the program is working effectively, and maintained it, when a new block when calling l stack redistribution.
Are accessible to the CPU program storage area for system store full, data blocks stored in DB, a local data store for the time being, peripheral I/O storage area (p), and so on.
Peripheral input (PI) and peripheral output (PO) stores besides the CPU model related to, and relevant to a specific module configuration of PLC application system, the maximum range is 64KB.