Description

The 6DD1606-4AB0​ is Siemens’ SIMADYN D IT42 I/O submodule​ — not a standalone PLC, but a plug-on expansion card seating on the CPU baseboards PM4, PM5, or PM6​ of the SIMADYN D drive-control family. Each 6DD1606-4AB0​ delivers 16 binary inputs, 16 binary outputs, 4 analog inputs (A/D, 12-bit), 4 integrating analog inputs (V/F — voltage-to-frequency for tacho/encoder), and 4 analog outputs, all funneled to the PM CPU through the local expansion bus and dual-port RAM at sub-µs latency — far tighter than any ET 200 remote-I/O rack over PROFIBUS could manage.What the datasheet doesn’t spell out — and what gets BOMs into trouble — is that the 6DD1606-4AB0​ itself carries zero field terminals. All 96 signals split across three 96-pin DIN headers (X6 = V/F AIN, X7 = A/D + AOUT, X8 = BI/BO) and land on SB/SU/SC interface modules​ mounted on the SIMADYN D rack’s wiring channel. Cloning a 6DD1606-4AB0​ into an old cabinet means matching the SB/SU/SC fit-out, not just the IT42. Siemens marked the 6DD1606-4AB0​ PM500 “deleted without replacement” from Oct 1, 2017 — today it lives purely as a brownfield spare SKU.

Application Scenarios

A cement-mill retrofit team in Southern Europe learned the SB/SU lesson the hard way. They’d sourced a 6DD1606-4AB0​ to replace a flaky IT42 on a PM5 rack driving a 4.8 MW cycloconverter-fed sync motor. The IT42 swapped in fine — 5 mins, PM5 recognized it, local-bus came up. But when they reconnected the three 96-pin DIN headers to the existing interface modules, the #3 A/D channel (one of the 4 × A/D, wired to a stator-current CT isolator on SC51) read -32767 full-scale. Turned out the original cabinet had used SC51-A​ (pin 27 = A/D ch3+, pin 28 = A/D ch3-) and the replacement 6DD1606-4AB0​ batch they’d received had left the factory tested against SC51-B​ — same 96-pin footprint, different pin-roll on the A/D bank. The fix was a 15-minute SC51 re-termination, but the “IT42 is just a spare” assumption cost them a 4-hour unplanned stop on the mill. The takeaway: the 6DD1606-4AB0​ is half the story; the SB/SU/SC interface modules are the other half, and a spare strategy that doesn’t cross-check both is incomplete.

Parameters