Key Technical Specifications
- Manufacturer: PROSOFT TECHNOLOGY
- Product Type: PROFIBUS DP Slave Communication Module
- Platform Compatibility: Allen-Bradley ControlLogix (1756 Backplane)
- Max Input Data: 122 Words
- Max Output Data: 122 Words
- Total Data Limit: 200 Words (Input + Output combined)
- Baud Rate: 9.6 kbps to 12 Mbps (Auto-baud supported)
- Physical Interface: DB-9F PROFIBUS Connector
- Node Address Range: 0 to 125
- Operating Voltage: 10 to 24 VDC
- Max Output Current: 1100 mA
Product Introduction
Integrating legacy PROFIBUS field devices into a modern Allen-Bradley ControlLogix system usually means dealing with protocol translation headaches. The PROSOFT MVI56-PDPS cuts through that mess. It plugs directly into the ControlLogix backplane and acts as a PROFIBUS DP slave, mapping field data straight into the processor’s memory using standard ladder logic.I’ve deployed these in petrochemical plants where we had to keep existing PROFIBUS valve manifolds running on a brand-new AB controller. The real value here is the 122-word data mapping limit per direction, which is more than enough for most I/O-heavy slave applications. Just be aware that the combined input and output cannot exceed 200 words total. This module is incredibly reliable once configured correctly, but the ProSoft Configuration Builder software has a learning curve. Take the time to read the manual, or you’ll be staring at a flashing red COMM fault light for hours.
Quality SOP & Tech Pitfalls
We don’t just pull these out of a bin and ship them. Every MVI56-PDPS goes through a rigorous bench test. First, we do a visual inspection to check for blown capacitors or damaged DB-9 pins. Then, it gets mounted on our live 1756 ControlLogix test rack. We run the ProSoft Configuration Builder to download a test config, verify the 24VDC backplane draw, and confirm the module successfully maps dummy data to the processor tags. We use a Fluke multimeter to verify the 10-24VDC input tolerance before sealing it in anti-static packaging.Here is where guys mess up: Do not ignore the 200-word total limit. I’ve seen engineers map 122 words of inputs and 122 words of outputs, push the config to the module, and wonder why the PROFIBUS network drops. The module will fault because 244 exceeds the 200-word hardware ceiling. Also, always take a photo of the DB-9 termination resistor settings and node address DIP switches before pulling the old module. If you lose your physical address, you’re locked out of the network until you reconfigure it.
Installation & Configuration Guide
- Pre-Installation Safety: ⚠️ POWER DOWN THE RACK. While ControlLogix supports some hot-swapping, communication modules are best installed with the backplane de-energized to prevent logic controller faults. Take clear photos of the old module’s DB-9 wiring and any external termination jumpers.
- Removal: Release the top and bottom locking tabs on the 1756 chassis. Pull the module straight out. Never pry it with a screwdriver, as this can bend the backplane pins.
- Installation: VERIFY DIP SWITCH AND JUMPER SETTINGS BEFORE INSERTING. Ensure the PROFIBUS node address matches your network design. Slide the MVI56-PDPS into the designated slot until the locking tabs click. Connect the DB-9 cable, ensuring the shield is properly grounded to the connector shell.
- Power-On & Testing: Power up the 1756 chassis. Watch the module LEDs; you should see a boot sequence followed by a solid green COMM indicator once the AB processor recognizes it. Open RSLogix 5000, verify the custom tags are updating, and force a test output to confirm the PROFIBUS master is receiving data.
Compatible Replacement Models
| Model | Compatibility Tier | Notes |
|---|---|---|
| MVI56-PDPS | ✅ Drop-in Replacement | Exact match. Standard PROFIBUS DP Slave. |
| MVI56E-PDPS | ⚠️ Software Compatible | Enhanced “E” series. Same physical footprint, but requires newer firmware and updated ProSoft Configuration Builder files. |
| MVI56-PDPMV1 | ❌ Hardware Mod Required | This is a PROFIBUS DP Master module. Do not buy this if your AB PLC is supposed to be the slave on the network. |
Frequently Asked Questions (FAQ)
Can I use this module if my ControlLogix processor is the PROFIBUS Master?
No. The MVI56-PDPS is strictly a Slave device. If your AB PLC needs to poll other PROFIBUS devices (like drives or remote I/O), you need the MVI56-PDPMV1 Master module instead.What happens if I exceed the 200-word combined data limit?
The module will fail to synchronize with the PROFIBUS master. You will likely see a configuration fault LED on the module, and the AB processor will flag a major communications fault. Keep your input and output mapping under the 200-word combined ceiling.Do I need a special license to configure this module?
Yes. You need the ProSoft Configuration Builder software (and often a specific license key depending on the version) to edit the PROFIBUS GSD file and map the data tables. You cannot configure this purely inside RSLogix 5000.Is this module compatible with Logix 5000 v32+ firmware?
Be careful here. Older MVI56 modules (pre-2008) can have compatibility issues with newer Logix 5000 firmware revisions. Always verify the hardware revision and firmware version of the MVI56-PDPS against your specific ControlLogix processor firmware before purchasing.Can I route Ethernet to configure this module?
Yes, if your ControlLogix chassis has an ENBT or EN2TR Ethernet module, you can enable CIPconnect™. This allows you to configure and monitor the MVI56-PDPS remotely via the ProSoft Configuration Builder without needing a direct serial cable to the module.The COMM LED is flashing red. How do I troubleshoot?
A flashing red COMM LED usually means the module is powered but not communicating with the PROFIBUS master. Check your baud rate settings, verify the node address matches the master’s configuration, and ensure the DB-9 termination resistors are set correctly at both ends of the bus.
