Product Overview

The 6ES5095-8MC01​ is Siemens’ SIMATIC S5-95U compact central processing unit—the “all-in-one” member of the S5-90U/95U/100U compact PLC family that Siemens sold through the late 1980s to late 1990s and eventually retired as the S5 platform went end-of-life. Where a full S5-115U/135U/155U needs a separate rack, power supply, CPU, and I/O modules, the 6ES5095-8MC01​ collapses the whole idea into a single 145 × 135 × 146 mm DIN-rail housing: the CPU, 24 V DC supply input, 16 digital inputs, 16 digital outputs (24 V DC source type, 0.5 A/point, short-circuit protected), 8 analog inputs, 1 analog output (0–10 V / 0–20 mA — the S5-95U 1AO can be switched between voltage and current range depending on wiring; the 8AI are typically 0–10 V single-ended), 4 interrupt/alarm DI (also usable as normal DI), and 2 counter DI are all onboard, plus two AS511 programming/communication interfaces on the front. The “-8MC01” suffix specifically means two programming interfaces (one for PG, one for OP/terminal) and two AS511 ports—no Profibus, no DP; that distinguishes it from the “-8MBxx” sub-variant (1 prog interface + Profibus) and the “-8MDxx” (Profibus DP slave) and “-8ME01” (L2 DP master) sisters. Siemens lists the 6ES5095-8MC01​ as “Compact PLC-unit, with 2 prog.-interface … with 2 interfaces AS511, w/o connector A, backup-battery”—the “connector A” remark means the front 20-pin flat-cable connector (for IM315 expansion or PG/OP dressing) ships separate, not in the box.Inside, the 6ES5095-8MC01​ carries 8 K statement internal RAM for STEP 5 programs, ~2 μs binary operation execution, 128 timers (0.01–9990 s), 128 counters (0–999, 8 retentive), 2048 flags (512 retentive), and a lithium backup battery (3.4 V / 850 mAh, ~5 yr life at 25 °C) that holds the RAM when 24 V DC drops. External I/O expansion via the IM315 interface module (6ES5315-8MA11) pushes the reachable envelope to max 448 digital I/O and 32 analog I/O across parallel expansion racks—though most 6ES5095-8MC01​ installs live entirely on the onboard I/O because the compact form factor is the point. For obsolescence buyers, the 6ES5095-8MC01​ is squarely a brownfield spare: it runs small German-built OEM machines, pump skids, compressor interlocks, and building-services panels commissioned 1990–1998 that nobody wants to re-engineer because “it works, don’t touch it.” When the backup battery dies unnoticed and the 24 V rail blips, the STEP 5 program in RAM vanishes—and suddenly the 6ES5095-8MC01​ needs a spare, a PG720, and someone who still remembers STEP 5.

Technical Specifications

Main Features and Advantages

Dual AS511 ports — PG and OP simultaneously.​ The defining trait of the 6ES5095-8MC01​ versus its -8MBxx and -8MDxx siblings is the two AS511 front interfaces. AS511 is Siemens’ S5-era serial programming protocol (RS-232 electrical, Siemens-private framing) that lets a PG720/PG740/PG685 programming terminal or a PC with STEP 5 + AS511 adapter upload/download/monitor. Having two ports means you can leave an OP (operator panel, e.g., Siemens OP7/OP17 on AS511) permanently connected on one port and still hang a PG or laptop on the other for online changes—no unplugging the HMI to tweak the ladder. The -8MBxx variants trade one of those AS511 ports for a Profibus interface; the -8MDxx swaps both for Profibus DP-slave; the 6ES5095-8MC01​ keeps both AS511, making it the right pick for standalone machines where the only “network” is a local OP panel, not a PLC-to-PLC Profibus.Onboard mixed I/O, no rack tax.​ A bare 6ES5095-8MC01​ gives you 16 DI + 16 DO + 8 AI + 1 AO + 4 alarm + 2 counter straight out of the box—enough for a small conveyor zone, a compressor-skids pressure/temp monitor + starter interlock, a pump-alternation panel with level transducer, or a small packaging-machine sequence with photo-eye DI, pneumatic valve DO, and an analog temperature read. No IM rack, no PS, no separate SM module—just DIN-clip the 6ES5095-8MC01, land 24 V DC, terminate the sensors and loads on the removable front connectors (Connector A sold separately, Siemens part for the 20-pin flat-cable dressing), and you’re running. For OEMs building 50 identical small machines, the 6ES5095-8MC01​ BOM is three lines: CPU, connector A, backup battery. That simplicity is why S5-95U fleets still run in German Mittelstand shops thirty years later.8 K STEP 5 statements and deterministic scan.​ The 6ES5095-8MC01​ isn’t trying to be an S7-1500—8 K statements is plenty for ladder logic that sequences 20–30 rungs with timers, counters, and a few analog compares. Execution at ~2 μs per binary op and scan-time monitoring (~300 ms watchdog) keeps things predictable; 128 timers and 128 counters onboard means you rarely need a counter/ timer expansion submodule (unlike S5-90U which is more constrained). Flags 2048, data blocks 2–255, PB/FB/SB all available—the 6ES5095-8MC01​ runs the full S5 block model (OB1/OB3/OB13/OB21/OB22/OB31/OB34/OB251, PB 0–255, FB 0–255 + integrated 240–243/250/251, SB 0–255), so code written on a bigger S5-115U can usually be trimmed and dropped onto the 6ES5095-8MC01​ with minor adaptation if I/O counts fit.IM315 expansion path for growth.​ When onboard isn’t enough, the front “Connector A” 20-pin flat-cable port on the 6ES5095-8MC01​ dresses to an IM315 (6ES5315-8MA11) parallel interface module, which in turn fans out to S5-95U expansion racks—max 448 digital I/O and 32 analog I/O across the extended plant. Most 6ES5095-8MC01​ installs don’t use this (the compact appeal is “no expansion”), but it’s there for the odd machine that grew a second conveyor line three years after commissioning and the OEM just daisy-chained an IM315 + two more DI/DO racks rather than re-PLC to S7-1200.Backup battery discipline.​ The 6ES5095-8MC01​ program lives in volatile RAM backed by that 3.4 V / 850 mAh lithium coin—Siemens quotes min 1 yr, ~5 yr @ 25 °C, but in a cabinet at 45 °C the life halves. When the battery dies and someone cycles the 24 V DC isolator, the STEP 5 program is gone and the 6ES5095-8MC01​ comes up with all outputs off and a flashing-battery LED (if the front indicator is still legible—some S5-95U fronts yellow badly after decades). The mitigation: annual PM swap the battery, and keep a printed/floppy/PG archive of the STEP 5 project. For plants that lost the archive, the 6ES5095-8MC01​ still allows an online upload while the battery is alive and 24 V is stable—do it now, not when the LED starts flashing.Legacy posture.​ S5 is fully discontinued; Siemens support for S5-95U manuals lives in the “S5 Old Testament” archive on support.industry.siemens.com. New projects are S7-1200 G2 / S7-1500, but the 6ES5095-8MC01​ remains buyable on the legacy-aftermarket because the installed base is still large in DACH machine shops, water-pumping stations, and 1990s-vintage building HVAC panels. The -8MC01 specifically is the “clean” AS511-only variant—if your panel has a 6ES5095-8MC01​ and someone asks “can we hang Profibus on it?” the answer is no, you’d need -8MB04 (Profibus interface, 1 prog port) or -8MD01 (DP-slave) or -8ME01 (DP-master) instead; don’t force a Profibus cable onto an AS511 port.