Product Overview
The SIEMENS 6ES5308-3UC21 is a PROFIBUS DP master interface module belonging to the IM 308-C family, engineered by Siemens to transform SIMATIC S5-115U, S5-135U, and S5-155U programmable controllers into powerful PROFIBUS DP masters capable of orchestrating large-scale distributed I/O architectures. As the revised version of the original IM 308-C (predecessor order number 6ES5 308-3UC11), the SIEMENS 6ES5308-3UC21 incorporates a new hardware platform that delivers enhanced performance while maintaining full functional compatibility with its predecessor when programmed via COM PROFIBUS up to V3.3. The SIEMENS 6ES5308-3UC21 serves as the critical communications bridge between legacy S5 central racks and the modern PROFIBUS DP fieldbus ecosystem, enabling seamless integration of ET 200 distributed I/O stations, S5-95U/DP nodes, drives, valves, and a vast array of field devices under a single deterministic network.
Positioned as a master interface module within the SIMATIC S5 intelligent interface portfolio, the SIEMENS 6ES5308-3UC21 occupies one slot in the central rack and draws 5V DC power directly from the S5 backplane bus, consuming a maximum of only 30mA. With a transmission rate scalable from 9.6kbit/s up to 12Mbit/s, the SIEMENS 6ES5308-3UC21 supports real-time data exchange critical for time-sensitive automation tasks. The module’s exceptional data capacity—13KB input and 13KB output address space with up to 244 bytes of user data per DP slave—accommodates high-density distributed I/O configurations that rival modern control system capabilities. The PROFIBUS DP interface on the SIEMENS 6ES5308-3UC21 is galvanically isolated, ensuring robust noise immunity and protecting the S5 rack electronics from field-side electrical disturbances.
Although Siemens officially discontinued the SIEMENS 6ES5308-3UC21 as part of the broader SIMATIC S5 product line, it remains an absolutely mission-critical spare part for thousands of industrial facilities worldwide that continue to rely on S5-based automation for their daily operations. The module requires a separately ordered 5V memory card (such as the 6ES5374-1KH21) to store DP master configuration data—a deliberate design decision in the revised hardware that enhances system reliability. For plant engineers managing legacy S5 installations, the SIEMENS 6ES5308-3UC21 is not merely a communication module; it is the lifeline that connects decades-old control architectures to contemporary fieldbus networks, enabling gradual modernization without wholesale system replacement.
Technical Specifications
| Parameter | Value |
|---|---|
| Product Model | SIEMENS 6ES5308-3UC21 |
| Manufacturer | Siemens AG |
| Product Type | SIMATIC S5 IM 308-C PROFIBUS DP Master Interface Module |
| Predecessor Model | 6ES5 308-3UC11 (IM 308-C original version) |
| System Compatibility | SIMATIC S5-115U, S5-135U, S5-155U central racks |
| Interface Physics | 9-pin Sub-D female (PROFIBUS connector) |
| Protocol Support | PROFIBUS DP Master (primary), PROFIBUS DP Slave (configurable) |
| Transmission Rate | 9.6kbit/s to 12Mbit/s (incl. 45.45kbit/s for PROFIBUS PA) |
| Maximum DP Slaves | 122 (ET 200 U/B, S5-95U/DP, and other field devices) |
| Address Range (Inputs) | 13 KB maximum |
| Address Range (Outputs) | 13 KB maximum |
| User Data per DP Slave | 244 bytes maximum (long consistency via FB192) |
| PROFIBUS Address Range | 1-123 (or 119 with P-page, 107 with Q-page addressing) |
| Supply Voltage | 5V DC via S5 backplane I/O bus |
| Current Consumption (5V) | Max. 30mA |
| Memory Card | 5V memory card required (e.g., 6ES5374-1KH21 256KB or 6ES5374-1KK21 1MB); 12V cards NOT supported in version 1+ |
| Interface Isolation | Galvanically isolated PROFIBUS DP interface |
| Configuration Software | COM PROFIBUS up to V5.0 (order no. 6ES5 308-3UC11), STEP 7 for slave-only config |
| Function Blocks | FB192 for long consistency, simplified diagnostics, SYNC/FREEZE commands |
| Dimensions (W×H×D) | 160 × 233.4 × 23 mm |
| Weight | Approximately 500g |
| Operating Temperature | 0°C to +60°C |
| Storage Temperature | -40°C to +70°C |
| Relative Humidity | Max. 95% at +25°C |
| Protection Rating | IP20 (for installation in module rack) |
| Firmware Versions | Release 1-11, V1.0 to V3.5; Release 6+ supports firmware update via memory card |
| Lifecycle Status | Discontinued by manufacturer; available as new surplus / refurbished spare part |
