Siemens SIMATIC S7-300 CPU

Description

• CPU 314C-2​ (6ES7314-6EH04 / 6ES7314-6CH04) → “C” = Compact​ — built-in 24 DI + 16 DO + 5 AI + 2 AO + 4 high-speed counters + 2 PTO/PWM​ on the CPU itself (no SM modules needed for small I/O counts). The difference: -6E​ = MPI/DP + PROFINET (PN) port​ (2-port switch integrated); -6C​ = MPI/DP only​ (no PN). The “4AB1” vs “4AB2” suffix: 4AB1 = single CPU only; 4AB2 = Starter Kit​ (CPU + MMC card + front connector + documentation) — verify at order time if you need the kit or bare CPU.
• CPU 315T-2 DP​ (6ES7315-7TJ10-0AB0) → “T” = Technology CPU​ — adds motion control / positioning / camming​ capability (up to 8/16 axes depending on config) via integrated technology functions (S7-300 + Technology — predecessor to S7-1500T). Has MPI/DP port, no PN on this p/n (TJ10 = DP-only). Requires STEP 7 + S7-Technology package​ (or TIA Portal with Technology objects) to program axes. Typical: single-axis positioning, cam plates, synchronous operation with servo drives (eynchronized via PROFIBUS DP to SINAMICS S120 etc.).
• CPU 317T-2 DP​ (6ES7317-7TK10-0AB0) → “T” Technology, but 317-class​ = bigger program/data memory than 315T (512 KB pg / 512 KB data vs 315T’s 384 KB / 384 KB) — supports more axes (up to 32 axes with FM 355 / via PROFIBUS to S120), more PID loops, more complex motion. Also MPI/DP only on this p/n (no PN).
• CPU 318-3 PN/DP​ (6ES7318-3EL01-0AB0) → 6ES7318​ is the flagship of S7-300​ — program memory 1 MB, data 2 MB​ (largest in S7-300, approaching S7-400 low-end). -3E​ = MPI + PROFINET (2-port switch) + PROFIBUS DP​ (3-port combo). No “C” built-in I/O (unlike 314C). This is the go-to when 315/317 hits memory or comms limit. Often used as central CPU for large S7-300 racks (ET200M remote I/O via IM360/361 or IM153-4 PN).

⚠️ Legacy Status: S7-300 is mature/legacy​ — new designs should use S7-1500​ (6ES7511/512/513…). But S7-300 installed base is enormous (automotive, water, pharma, food, steel, cement). If you need spares / repair / keep-production-running​ → these p/n are correct. If new design​ → migrate to S7-1500 (different rack/form factor — S7-300 = 40mm module width, S7-1500 = 25/35mm; program migrates via TIA Portal “Migrate Project” ~80% auto-convert, rest manual — S7-300 → S7-1500 migration guide available from Siemens).

💡 MMC Card Required!: All S7-300 CPUs (from the “C” generation onward, i.e., 314C/315/317/318-3) require a MMC (Micro Memory Card, 6ES7953-8…) to store the program​ — no MMC = CPU won’t go to RUN (will fault SF/BF). The CPU itself has no permanent program storage. Typical MMC sizes: 128KB (6ES7953-8LG30-0AA0), 512KB (8LJ30), 2MB (8LL30), 4MB (8LM30), 8MB (8LP30). Choose ≥ your program+data size. 4AB2 kits include MMC; 4AB1 bare CPU does NOT.

Key Features (by sub-family)

• CPU 314C-2 PN/DP (6ES7314-6EH04): Compact CPU — built-in 24 DI + 16 DO (24V DC transistor/sink-source) + 5 AI (12-bit) + 2 AO (12-bit) + 4 HSC (max 60 kHz) + 2 PTO (pulse train for stepper/servo) — no extra SM modules for small machine. MPI/DP + PN (2-port switch). Program memory 192 KB.
• CPU 314C-2 DP (6ES7314-6CH04): Same built-in I/O as EH04, but no PN​ — only MPI/DP. Cheaper if PN not needed.
• CPU 315T-2 DP (6ES7315-7TJ10): Technology CPU — 384 KB pg / 384 KB data. Motion control up to 8 axes (cam, positioning, interpolation) via S7-Technology. MPI/DP only.
• CPU 317T-2 DP (6ES7317-7TK10): Technology CPU — 512 KB pg / 512 KB data. More axes (up to 32 with expansion), more complex motion. MPI/DP only.
• CPU 318-3 PN/DP (6ES7318-3EL01): Flagship S7-300 — 1 MB pg / 2 MB data. MPI + PN (2-port) + DP. Largest S7-300 — central host for big racks / ET200M remote I/O. No built-in I/O (unlike 314C).
• Country of Origin: Germany / EU (Siemens AG)

Model & Variant Reference (Your List Decoded)

⚠️ Critical Notes:

1. 4AB1 vs 4AB2 (314C): 4AB1 = bare CPU only​ (no MMC, no front connector, no manual). 4AB2 = Starter Kit​ (CPU + MMC card + front connector 40-pin + documentation). If replacing a failed CPU in existing rack — you may only need 4AB1 (reuse existing MMC/front conn). If new build / spare — 4AB2 kit saves sourcing MMC separately. MMC is mandatory​ for 314C/315/317/318 to RUN.
2. 314C “C” = Compact = Built-in I/O: Unlike 315/317/318 which are “naked CPUs” (all I/O via SM321/322/331/332), the 314C has 24 DI + 16 DO + 5 AI + 2 AO on-CPU​ — for small machines (packaging, labeling, small conveyor) you can skip SM modules entirely. The 4 HSC + 2 PTO make it great for simple stepper/servo positioning without Technology CPU.
3. 315T / 317T “T” = Technology / Motion: These are NOT​ general-purpose CPUs — they’re for axis control​ (positioning, cam plates, synchronous operation with SINAMICS S120 via PROFIBUS DP). Programming requires STEP 7 + S7-Technology package​ (or TIA Portal with Technology objects). If you don’t need motion, buy plain 315-2 PN/DP (6ES7315-2EH14-0AB0) — cheaper. 315T/317T are pricier.
4. 318-3 is the S7-300 Ceiling: 318-3EL01 has PN + DP + MPI​ — 1 MB pg / 2 MB data. When your 315-2 (384KB) or 317-2 (1MB) hits memory, or you need PN+DP+MPI all on CPU + big ET200M remote I/O — 318-3 is the answer. No built-in I/O (unlike 314C).
5. MMC Card Sizing: Rule — MMC must be ≥ program + data + overhead (leave ~30% headroom). For 314C (192KB pg) → 512KB MMC (6ES7953-8LJ30) is safe. For 318 (1MB pg + 2MB data = 3MB+ → need 4MB or 8MB MMC). Never pull MMC hot!​ — remove power first or CPU will fault.

Technical Specifications (Representative — 6ES7314-6EH04-4AB1, CPU 314C-2 PN/DP)

Warranty & After-Sales

• Factory new units: 12 months warranty
• Refurbished units: 3-6 months warranty (bench: insert into test S7-300 rack + PS307 → MMC with test program → go RUN → force DI (314C built-in) → monitor PIW/PQW (built-in AI/AO) → verify PN/DP ping)
• Technical support for:
  • 314C built-in I/O wiring​ (24 DI on CPU front connector 40-pin — pinout: DI 0.0–2.7 = 24V DC sink/source; 16 DO transistor 0.5A; 5 AI (0–10V/4–20mA); 2 AO — refer to 6ES7314-6EH04 manual pin map)
  • MMC card selection​ (128KB/512KB/2MB/4MB/8MB — 314C needs min 512KB MMC; 318 needs 4MB+; 4AB2 kit includes MMC, 4AB1 bare does NOT)
  • 4AB1 vs 4AB2 clarification​ (bare CPU vs Starter Kit — existing rack reuse: 4AB1 + reuse old MMC/front conn; new build: 4AB2 kit)
  • STEP 7 / TIA first connect​ (MPI cable PC-Adapter USB → CPU MPI port → set PG/PC interface → go Online → download HW Config + program; for PN: set temp IP via MPI first, then PN accessible)
  • 315T/317T motion setup​ (STEP 7 + S7-Technology package → Technology objects (TO_AXIS, TO_CAM) → SINAMICS S120 via DP/PN — requires know-how; we support basic commissioning questions)
  • 318-3 large-rack config​ (central S7-300 + ET200M remote via IM360/361 or IM153-4 PN — max I/O 1024/256)
  • Migration S7-300 → S7-1500​ (TIA “Migrate Project” ~80% auto, rest manual — if planning future migration, discuss with us)
• Optional: MMC cards (6ES7953-8LG30 128KB / 8LJ30 512KB / 8LL30 2MB / 8LM30 4MB / 8LP30 8MB), Front connector 40-pin (6ES7392-1AM00-0AA0 for 314C), PS307 (6ES7307-1BA00-0AA0 2A / 6ES7307-1EA00-0AA0 5A), S7-300 rack (6ES7390-1AE80), Battery (6ES7971-1AA00 — RTC backup), STEP 7 / TIA license, S7-Technology package (for 315T/317T)

Delivery Time

• Standard delivery: 3-5 working days (stock NOS)
• Express shipping available upon request

Why Choose Our Store

• Genuine Siemens SIMATIC S7-300 CPUs — not gray-market (MMC compatibility & PN PHY critical for plant)
• Global supply network with competitive pricing on S7-300 legacy spares (314C/315/317/318 all in stock)
• Expertise in S7-300 system composition (PS + CPU + SM + ET200M remote, 314C built-in I/O wiring, 315T/317T motion basics, MMC sizing)
• Comprehensive technical documentation (314C 40-pin front connector pinout, MMC size chart, TIA migrate S7-300→S7-1500 notes, 315T/317T SINAMICS S120 linkage sketch)
• Responsive customer service and support

Applications

• CPU 314C-2 (EH04/CH04) — Small-to-Mid Machine OEM: Built-in 24 DI + 16 DO + 5 AI + 2 AO + 4 HSC + 2 PTO = complete small machine in one CPU​ (packaging, labeling, small conveyor, feeder, pump skid). EH04 adds PN (connect to HMI/SCADA/Profinet drive directly). CH04 = DP-only, cheaper for DP-existing plants.
• CPU 315T-2 DP / 317T-2 DP — Motion / Positioning: Single/multi-axis positioning (cut-to-length, flying shear, cam press, rotary indexing). 315T → up to 8 axes simple; 317T → up to 32 axes complex. SINAMICS S120 via PROFIBUS DP for servo loop. Requires S7-Technology package.
• CPU 318-3 PN/DP — Large Central Rack / Process: When 315-2 (384KB) or 317-2 (1MB) hits memory, or you need PN+DP+MPI + ET200M remote I/O (IM360/361 or IM153-4 PN) — 318-3 is ceiling of S7-300 (1MB pg / 2MB data). Water treatment, bulk material, large process skids.
• Retrofit / Spare for Existing S7-300 Plants: Exact p/n match for failed CPU in existing rack (automotive, pharma, food & beverage, steel, cement — S7-300 everywhere since 2000s). MMC transplant: pull MMC from old dead CPU → insert into new → RUN (if same p/n family; if upgrading 314→315 etc., need program re-download).
• Migration Holdover: Many plants standardize on S7-300 spares for 10–20yr lifecycle — stock NOS CPUs as cold spare. Next major downtime → migrate to S7-1500 (TIA migration tool ~80% auto).