Application Scenarios
At a regional cement grinding plant running a SIMATIC S5-115U as the kiln-feed master, the original design used the CPU’s integrated I/O and a handful of digital modules — but no serial link. When the plant added a new truck-loading weighbridge (output: ASCII string @ 9600/8/N/1 on RS-232), the integrator didn’t want to replace the S5-115U or add an external gateway box that would need its own 24 VDC feed and panel space. Instead, they slotted a 3CP340 60-2 B R into rack slot 4 of the S5-115U, loaded the “ASCII driver” firmware option onto the CP via STEP 5, and wired the weighbridge’s DB-25 straight into the CP’s front connector. The 3CP340 handles character-level buffering and checksum framing in its own microcontroller, passing only the parsed weight value + timestamp into the CPU’s data block. Total panel-space cost: one Euro-card slot. The plant’s automation tech noted the retrofit took “one afternoon and zero DCS changes” — the S5 CPU just saw a new DB appear as if the weighbridge had always been there.
Parameters
| Main Parameters | Value/Description |
|---|---|
| Product Model | 3CP340 60-2 B R (Siemens 6ES5340-3CP40 aligned) |
| Manufacturer | Siemens |
| Product Category | Communications Processor (PTP Serial), S5 rack |
| Host System | SIMATIC S5-115U / S5-135U / S5-155U |
| Interface | V.24 / RS-232 (25-pin D-Sub front connector) |
| Baud Rate | 300 bps – 19.2 kbps (S5 CP340 class) |
| Protocols | ASCII (with handshake), 3964R, RK512 (loadable drivers) |
| Buffer | Internal character buffer (CP-side, offloads CPU scan) |
| Supply | 5 V DC from S5 rack backplane (+24 V DC for termination power, typical) |
| Power Draw | ~2–3 W (rack-powered, negligible) |
| Diagnostics | SF (fault), ACT (active) LEDs; STEP 5 diagnostic FB |
| Mounting | S5 Euro-card rack slot (backplane bus) |
| Operating Temp. | 0 °C to +60 °C (control-cabinet) |
| Handshake Lines | RTS/CTS, DSR/DTR, DCD (software-config via STEP 5) |
Technical Principles and Innovative Values
- Innovation Point 1: CPU-Offloaded Serial Buffering. The main S5 CPU (943/945/948) already carries the PID for kiln feed, belt speed, and baghouse draft — adding character-level UART interrupts to that load would stretch scan time. The 3CP340 60-2 B R has its own on-board microcontroller that handles start-bit/stop-bit detection, parity check, and buffer assembly. The S5 CPU only gets interrupted when a complete telegram (e.g., one ASCII line from the weighbridge) is ready, delivered via the S5 backplane into a designated DB. This keeps the main scan deterministic even when the serial line is chatty.
- Innovation Point 2: Loadable Driver Flexibility Without Hardware Change. The same 3CP340 60-2 B R hardware supports multiple Siemens loadable drivers: pure ASCII (printers, barcode, terminals), 3964R (Siemens PTP standard, often plant-internal), and RK512 (Siemens cross-PLC telegram). Switching from “talk to a printer” to “talk to a Modbus-RTU drive with a wrapper” is a firmware-load step in STEP 5, not a panel re-wire. For plants sitting on 30-year-old S5 spares, that flexibility keeps one SKU relevant across multiple subsystems.
- Innovation Point 3: Rack-Powered, Zero-Footprint Retrofit. Because the 3CP340 60-2 B R draws 5 VDC from the S5 backplane and only needs a front D-Sub for the serial pair, it consumes literally one rack slot and zero DIN-rail width. In a cramped S5-115U cubicle (often already packed with DI/AI/DO/AO cards), that “no new panel space” attribute is why many plants still buy 3CP340 units in 2025 instead of ripping the S5 out — the alternative (an external gateway + DIN PSU + terminal doubles) costs 3× and breaks the backplane determinism.
Application Cases and Industry Value
A municipal water-treatment works in the UK ran four S5-135U racks across raw-water intake, aeration, sludge, and outfall. The outfall rack needed to push hourly flow totals to a third-party telemetry box (RS-232, proprietary ASCII framing) mounted in the same MCC. Rather than spec a new S7-1500 remote station (CAPEX rejected), the utility engineer dropped a 3CP340 60-2 B R into the spare slot of the S5-135U, loaded the ASCII driver, and wrote ~40 lines of STEP 5 STL to format “FLOW=XXXX.X,MDate=DDMMYY” strings. The 3CP340 buffers each string and handles the telemetry box’s CTS/RTS handshake — the S5 CPU just writes the DB and sets a transmit-flag bit. The retrofit cost was under £400 all-in and has run 4+ years without a comms drop. The works’ senior tech: “The 3CP340 is the cheapest ‘keep the S5 alive another decade’ trick in the book.”
Related Product Combination Solutions
The 3CP340 60-2 B R sits in an S5 rack ecosystem. Common companions:
- 6ES5943 / 6ES5945 / 6ES5948 — S5-115U / 135U / 155U CPUs (e.g. CPU 943-1UB11, CPU 945-1UB11) that host the 3CP340 on the backplane.
- 6ES532x / 6ES533x — S5 digital/analog I/O modules (DI/DO/AI/AO) typically in the same rack as the 3CP340.
- 6ES546x (IM modules) — S5 Interface Modules for rack-to-rack expansion (EU 181/183); the 3CP340 often sits in the central rack talking out to field serial devices while IM modules handle local I/O expansion.
- 6ES7340-1… (S7-300 CP340) — The S7-300 successor if you’re migrating the S5-115U to S7-300; pin-compatible concept but different backplane — not a drop-in, but the functional equivalent.
- 6ES7341-1… (CP341) — S7-300’s smarter sibling (adds Modbus-RTU master/slave firmware natively); if the 3CP340 can’t quite carry your Modbus load on S5, CP341 on an S7-migration is the usual step-up.
- S5-95U / S5-100U — Smaller S5 racks; the CP340 also exists in compact versions for these, though the 3CP340 60-2 B R is typically the S5-115U/135U Euro-card variant.
