S5-115F Manual Technical Description
2.2 Principle of Operation of the Programmable Controller
This section describes how the PC processes your program.
2.2.1 Functional Units
Subunit A
I/O bus I/O bus
I/O modules
Internal
program
memory
(RAM)
ACCUM
Processor
Timers,
counters,
flags
PII PIQ
CPU
PIQ
Processor
Internal
program
memory
(RAM)
ACCUM
CPU
Timers,
counters,
flags
PII
Output modules
(digital / analog)
Input modules
(digital / analog)
Function
modules
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I/O modules
Input modules
(digital / analog)
Output modules
(digital / analog)
Function
modules
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Parallel interface
Memory
submodule
(EPROM/
EEPROM/
RAM)
Serial
inter-
face
Memory
submodule
(EPROM/
EEPROM)
Serial
inter-
face
Subunit B
Figure 2-2. Schematic Representation of the S5-115F
Program Memory
The control program is stored in the memory submodule ( 2.3.2) or in the internal RAM.
To safeguard against losing the program, dump it in an external EEPROM/EPROM memory sub-
module. In contrast to these memory submodules, the internal RAM or a RAM memory submodule
has the following characteristics:
• The memory contents can be changed quickly.
• User data can be stored and changed.
• When the power fails and there is no battery, the memory contents are lost.
In safety mode, the control program must be stored in the EEPROM/EPROM submodule. If no
memory submodule or another memory submodule is connected, the S5-115F switches auto-
matically into test mode.
EWA 4NEB 811 6148-02
2-3
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