Siemens SIMATIC S5 Communication Modules: 6ES5526-3LF01

Technical Dossier

Product Details And Specifications

Siemens SIMATIC S5 Series Technical Notes

The Siemens SIMATIC S5 programmable controller family represents one of the most widely deployed automation platforms in global heavy industry. Installed across petrochemical complexes, nuclear power stations, offshore refineries, and continuous-process manufacturing facilities from the early 1980s through the 2000s, the S5 series established the architectural baseline for modern DCS and PLC integration. The S5-115U, S5-135U, and S5-155U sub-families remain operational in thousands of brownfield sites where replacement with S7 or TIA Portal-based systems is constrained by capital expenditure cycles, regulatory freeze periods, or process criticality. The 6ES5526-3LF01 Communication Processor (CP 526) is a representative module of the S5-500 backplane ecosystem, providing point-to-point serial communication capability for host computer coupling and inter-PLC data exchange.

The Evolution of SIMATIC S5 Architecture

The SIMATIC S5 architecture was introduced by Siemens in 1979 and underwent iterative expansion across four decades. The original S5-100U addressed compact machine-level control; the S5-115U targeted mid-range process applications; the S5-135U and S5-155U addressed large-scale distributed control with multi-rack configurations and high-channel-count I/O. Communication capability evolved from proprietary SINEC H1 and L2 bus interfaces in the early 1980s to standardized PROFIBUS-DP adapters in the late 1990s. The CP 526 (6ES5526-3LF01) belongs to the serial communication processor generation, supporting 20 mA TTY and RS-232C interfaces for host coupling via the 3964/3964R and RK512 protocols. Compatibility constraints are significant: S5 modules are backplane-specific and cannot be interchanged across S5-100U, S5-115U, and S5-135U/155U racks without adapter hardware. Siemens officially discontinued the S5 product line in 2013, transitioning customers to the SIMATIC S7-300 and S7-400 platforms. However, field populations remain large enough that the aftermarket supply chain for S5 spare parts constitutes a distinct and active procurement category.

SIMATIC S5 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly sourced modules within the SIMATIC S5 ecosystem. Modules are classified by functional category.

Communication Processors (CP)

• 6ES5526-3LF01: CP 526 — serial CP for S5-135U/155U, 20 mA TTY / RS-232C, 3964R & RK512 protocol support
• 6ES5524-3UA15: CP 524 — serial communication processor, RS-232C, point-to-point host coupling for S5-115U
• 6ES5525-3UA21: CP 525 — serial CP with 20 mA TTY interface, S5-115U rack compatible
• 6ES5530-3LA12: CP 530 — SINEC L2 bus coupler, token-passing LAN interface for S5-135U/155U
• 6ES5535-3LA12: CP 535 — SINEC L2 DP master interface for S5-135U/155U distributed I/O coupling
• 6ES5541-3AD13: CP 541 — point-to-point CP, RS-422/485, for S5-115U, supports 3964R protocol
• 6ES5543-3AA11: CP 543 — Industrial Ethernet TCP/IP processor for S5-135U/155U, 10 Mbit/s

Central Processing Units (CPU)

• 6ES5948-3UA23: CPU 948 — high-performance 32-bit CPU for S5-155U, extended memory, multi-tasking
• 6ES5944-3UA11: CPU 944 — standard 32-bit CPU for S5-155U, 48 KB program memory
• 6ES5928-3UB21: CPU 928B — 32-bit CPU for S5-135U, 64 KB RAM, extended instruction set
• 6ES5926-3SA11: CPU 926 — 16-bit CPU for S5-135U, 32 KB program memory, standard processing
• 6ES5921-3WA13: CPU 921 — compact CPU for S5-115U, 16 KB RAM, standard I/O interface

Digital Input / Output Modules (DI / DO)

• 6ES5420-7LA11: DI 420 — 32-channel 24 VDC digital input module for S5-115U/135U racks
• 6ES5430-7LA11: DO 430 — 32-channel 24 VDC / 0.5 A digital output module, S5-115U/135U
• 6ES5451-7LA11: DI/DO 451 — 16-channel mixed I/O, 24 VDC, S5-115U compatible

Analog Input / Output Modules (AI / AO)

• 6ES5464-8ME11: AI 464 — 8-channel analog input, ±10 V / 4–20 mA, 12-bit resolution, S5-135U
• 6ES5470-8MA12: AO 470 — 4-channel analog output, ±10 V / 4–20 mA, 11-bit + sign, S5-135U

Power Supply Units (PS)

• 6ES5955-3LC41: PS 955 — 24 VDC / 15 A rack power supply for S5-135U/155U central racks
• 6ES5951-7LD21: PS 951 — 24 VDC / 10 A power supply for S5-115U expansion racks