SIEMENS 6ES5 375-0LD21

Siemens 6ES5 375-0LD21 SIMATIC S5 RAM Memory Module

Description

The Siemens 6ES5 375-0LD21 is a 16 KByte RAM memory submodule for the legacy SIMATIC S5 automation system. This module is essential for storing user programs and process data within S5-135U and S5-155U series controllers. As a volatile memory component, it relies on a backup battery to retain data during power-off conditions. It is a critical component for the maintenance and operation of existing S5-based industrial machinery.

Specifications

• Manufacturer: Siemens
• Product Series: SIMATIC S5
• Part Number: 6ES5 375-0LD21
• Module Type: RAM Memory Submodule
• Memory Capacity: 16 KByte (16K x 8 Bit)
• Compatibility: S5-135U, S5-155U PLCs
• Memory Technology: Static RAM (SRAM)

Label Info

• Brand: Siemens
• Model: 6ES5 375-0LD21
• Description: MEMORY SUBMODULE 16KX8BIT

Application

This memory module is used in various industrial automation applications controlled by Siemens S5-135U/155U systems, including manufacturing lines, process control, and material handling systems that were automated in the 1980s and 1990s.

Country of Origin

Made in Germany.

CO2 Impact

Choosing this reused Siemens memory module over a new alternative prevents an estimated 2.0 kg of CO2 emissions. This saving is comparable to the emissions from driving an average car for 10 kilometers.

Availability

This is an obsolete item, availability is limited to existing stock. Order now from spareparts2day for expert support and fast delivery.

FAQ

Is this module volatile? Will it lose its data when power is removed?

Yes, this is a RAM (Random Access Memory) module. It requires a backup battery on the S5 CPU rack to retain its program and data when the main power is off. Without a functional backup battery, the memory will be erased upon power loss.

What is the difference between this RAM module (6ES5 375-0LD21) and an EPROM or EEPROM module for the S5?

This RAM module allows for easy and fast program changes directly from the programming device. EPROM (Erasable Programmable Read-Only Memory) and EEPROM (Electrically Erasable…) modules are non-volatile, meaning they hold their program without battery backup. This RAM module is ideal for program development and applications where data is frequently updated.

Which specific Siemens S5 PLCs are compatible with the 6ES5 375-0LD21 module?

This memory submodule is specifically designed for the higher-end Siemens SIMATIC S5-135U and S5-155U programmable logic controllers. It is not compatible with smaller S5 systems like the S5-95U or S5-115U. Always verify compatibility with your specific CPU model’s technical manual.

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Last Update: Friday, March 13, 2026