Product Overview
The Siemens 6DD1606-3AC0 is a SIMADYN D IT41 technology submodule — the analog+encoder+binary I/O daughter module that plugs onto a PM5 or PM6 CPU module inside a SIMADYN D rack, occupying one additional slot beside the CPU (maximum two ITxx submodules per PM5/PM6). Unlike the passive EM11/EM12 binary I/O modules that sit as standalone rack slots, the 6DD1606-3AC0 carries its own 32-bit RISC coprocessor with 1 MB Flash, 2 MB RAM and 32 KB EEPROM, plus two serial interfaces and SSI encoder support — it is not just an I/O expander but a preprocessing node that offloads encoder decoding, alarm input capture, and analog buffering from the PM6’s D7-SYS scan. The 6DD1606-3AC0 communicates with the host PM6 over the L-bus backplane, with the PM6 reading IT41’s dual-port buffer at the configured task cycle (typically 0.5 ms) while the IT41’s RISC continuously scans its 4 AI, 4 AO, 16 BI, 16 BO, and 4 incremental encoder channels independently.
Channel-wise, the Siemens 6DD1606-3AC0 delivers 4 analog inputs (±10 V / ±20 mA range, 13-bit resolution typical) and 4 analog outputs (±10 V), 16 bidirectional 24 V DC binary inputs/outputs, and 4 incremental encoder inputs with monitoring tracks — each encoder channel gets one alarm input (e.g., encoder fault, overspeed trip) and one alarm reset output, making the 6DD1606-3AC0 directly suitable for axis-safety and cam-position capture without burning PM6 interrupt budget. The encoder section supports 2-track 90° displaced (A/B + optional Z zero-pulse), 5 V / 15 V push-pull or RS-422, forward/reverse pulse counting — the IT41 RISC decodes quadrature and holds position/velocity registers that the PM6 picks up over L-bus. One of the two serial ports can alternatively host an SSI absolute encoder (or both serials host two SSI encoders depending on configuration), extending the 6DD1606-3AC0 into absolute-position skids (press slide, hydraulic ram).
In the SIMADYN D rack ecosystem, the Siemens 6DD1606-3AC0 is the most common technology submodule pairing with a PM6 (6DD1600-0AK0) on tandem-mill stands, compressor antisurge skids, and servo-hydraulic test rigs — the PM6 closes tension/position/ surge loops at 0.5 ms while the IT41 fronts the sensors: strip-tension transducer (AI), looper-angle LVDT (AI), screw-down position ±10 V (AO to valve), stand-motor incremental encoder (Encoder Ch1), looper-motor encoder (Ch2), reel-diameter encoder (Ch3), and a spare (Ch4). The 16 BI/BO handle valve limit-switches, “ready” from drive, emergency-capture, and local lamp drivers.
Lifecycle: the Siemens 6DD1606-3AC0 went PM500, discontinued 1 Oct 2017, deleted without replacement per Siemens Industry Mall — same fate as the CS8 carrier we covered prior. There is no SINAMICS/TDC submodule that drops onto a PM6; the only forward path is full rack migration (PM6+IT41 → S7-1500T + ET 200 + TM54F encoder modules). Thousands of SIMADYN D racks still run IT41s, so the 6DD1606-3AC0 is purely spare-demand today, and because it’s a “daughter submodule” not a rack slot, many plants underestimate spares — they stock PM6 and CS8 but forget the that sits on the PM6, until one encoder channel drifts and the whole stand’s tension PI floats.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 6DD1606-3AC0 |
| Manufacturer | Siemens |
| Product Type | SIMADYN D Technology Submodule (plugs onto PM5/PM6 CPU) |
| Mounting | Daughter submodule on PM5/PM6; occupies 1 additional rack slot; max 2 ITxx per CPU |
| Onboard Processor | 32-bit RISC |
| Memory | 1 MB Flash / 2 MB RAM / 32 KB EEPROM |
| Analog Inputs | 4 (±10 V / ±20 mA, 13-bit typ.) |
| Analog Outputs | 4 (±10 V) |
| Binary I/O | 16 BI / 16 BO, 24 V DC, bidirectional |
| Encoder Inputs | 4 incremental (2-track A/B + Z optional), 5 V / 15 V push-pull or RS-422 |
| Encoder Alarm | 1 alarm input + 1 alarm reset output per encoder channel |
| SSI Encoder Support | Via serial interface (1 or 2 SSI, config-dependent) |
| Serial Interfaces | 2 (one substitutable with SSI) |
| Backplane Bus | L-bus (to PM5/PM6 host) |
| Supply Voltage | +5 V / +24 V via PM5/PM6 backplane (from rack EB1) |
| Operating Temperature | –25 … +60 °C |
| Storage Temperature | –40 … +85 °C |
| Protection Class | IP20 |
| Dimensions (W × H × D) | 20.14 × 233.4 × 220 mm |
| Weight | 0.6 kg |
| Configurable With | D7-SYS (SIMADYN D engineering toolchain) |
| Lifecycle Status | PM500 – Discontinued 1 Oct 2017, deleted without replacement |
Main Features and Advantages
Technology submodule with own RISC — not passive I/O
The biggest differentiator of the Siemens 6DD1606-3AC0 versus a rack-slot I/O module (EM11/EM12) is that the carries a 32-bit RISC processor, 1 MB Flash, 2 MB RAM, and 32 KB EEPROM of its own. It is not a dumb register-map that the PM6 polls — the RISC continuously scans its 4 AI via onboard ADC, drives its 4 AO DACs, samples 16 BI at hardware rate, refreshes 16 BO from L-bus writes, and decodes 4 quadrature encoders into 32-bit position + 32-bit velocity registers locally. The PM6 reads the ‘s dual-port RAM over L-bus at the 0.5 ms task cycle and finds pre-decoded encoder position, pre-averaged AI, and BI edge-flags already there. On a 5-stand tandem mill where Stand 2 PM6 runs tension PI (FB401) + looper torque (FB402) + screw-down hydraulic (FB420), offloading encoder decode (4 axes × quadrature) and AI averaging (4 tension transducers × 2 kHz sample) to the 6DD1606-3AC0 keeps the PM6’s 0.5 ms scan clean — a pure-passive-I/O design would burn 30–40% of the PM6 scan just moving ADC words.