Description

The 6ES5304-3UB11​ is a Siemens SIMATIC S5 IM 304 “Connection Interface Module” designed to link a S5 central rack (CR) to one or more distributed expansion units (EU) across the S5 parallel system bus, using the dedicated 721-series flat cable. It belongs to the S5-115U / S5-135U / S5-155U ecosystem and is the classic CR-side enabler that lets I/O live hundreds of meters away from the CPU instead of being crammed into the same. The 6ES5304-3UB11​ draws 5 V from the S5 backplane and requires an auxiliary 24 V DC feed (via front connector or rack power supply) to drive the bus transceivers over distance; configuration is handled through onboard jumpers (X11 for total cable length, X21/X22 for per-interface enable) and the S3 DIP block, all manageable inside the live rack without a PG once the hardware map is known.

Application Scenarios

A cement-plant raw-mill line still running an S5-155U central rack in the main MCC room, the original I/O was all local — until a 2012 upgrade added a bag-filter pulse-jet station 180 m away across the catwalk. Cramming 120 DI + 80 DO into the MCC-room rack would have meant a second S5-115U CPU and a Profibus link (the plant never adopted Profibus on S5 consistently), so the integrator dropped dropped an EU 701-3 expansion rack at the bag-filter end and paired it with a 6ES5304-3UB11​ in the S5-155U CR (slot adjacent to the CPU) and an IM 314 in the EU rack. The 721 flat cable ran the existing tray (already carrying 230 V motor feeds — the Siemens-shielded 721 version handled the EMC fine once grounded at both ends). Jumper X11 on the 6ES5304-3UB11​ was set to the 200 m range (the 180 m run + 15 m internal EU harness), X21/X22 both ON, S3 all-ON per the Siemens distributed-config diagram. Because the IM 304/314 pair carries address, data, and interrupt transparently, the bag-filter I/O maps straight into the S5-155U’s process image — no DP mapping, no GSD, no extra OB-call. The plant EE’s comment: “it’s the only S5 extender that doesn’t feel like a network.” Twelve years on, the same 6ES5304-3UB11​ is still in the CR; they keep one 6ES5304-3UB11​ and one IM 314 on the spares cage because the S5 is staying until the line’s full PCS 7 migration in 2027.

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