SST 5136-DNP | DNP 3.0 Communication Module for ControlLogix

Description

Product Introduction

That water utility in Arizona—the one with the remote pumping stations spread across the desert—had a SCADA communication failure last summer. The ControlLogix PLC at the main plant couldn’t talk to the remote RTUs anymore. The IT guys blamed the radios, the SCADA guys blamed the PLC program. I drove out, plugged into the SST 5136-DNP module in the ControlLogix rack. The serial port LEDs were flickering, but the “DNP COMM” LED was dark. Pulled the module, reseated it, same thing. Swapped it with a spare, reconfigured the DNP addresses, and the SCADA link came right up. The old module had a dead UART—silent failure, no alarms, just no communication.

The SST 5136-DNP is a DNP 3.0 protocol module that plugs directly into a Rockwell Automation ControlLogix or CompactLogix chassis. It handles all the DNP 3.0 protocol overhead—frame assembly, error checking, time synchronization—so the PLC processor doesn’t have to. The module can act as a DNP master (polling remote RTUs) or a DNP slave (responding to a SCADA master). It has two serial ports (configurable for RS232 or RS485) and, depending on the variant, an Ethernet port for DNP 3.0 over TCP/IP (the 5136-DNP-104 version). In the water/wastewater world, this module is the bridge between the PLC and the SCADA system. Without it, the operator in the control room can’t see pump status or change setpoints.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

A comms module gets a full protocol test. Here’s our process.

1. Incoming Verification
   • Match the model: 5136-DNP. (Check if it’s the -104 Ethernet version.)
   • Visual inspection: Look for bent pins on the backplane connector. Check the serial port connectors—no bent pins.
   • Inspect the PCB—no corrosion, no burn marks.
2. Power-On Self-Test
   • Install the module in a ControlLogix test rack with a known-good processor and power supply.
   • Apply rack power—watch the “OK” LED.
   • Connect to the module via serial or Ethernet using SST’s configuration software.
   • Verify the module is recognized and passes its internal diagnostics.
3. Serial Port Test
   • Connect a serial loopback plug to port 1.
   • Run a serial test from the configuration software—verify data is sent and received correctly.
   • Repeat for port 2.
   • Test both ports at multiple baud rates (9600, 19200, 38400).
4. DNP Protocol Test (Master Mode)
   • Configure the module as a DNP master.
   • Connect to a DNP slave simulator (we use a laptop running a DNP test tool).
   • Poll the slave for analog inputs, binary inputs, and counters.
   • Verify all data is transferred correctly.
   • Test unsolicited responses from the slave.
5. DNP Protocol Test (Slave Mode)
   • Configure the module as a DNP slave.
   • Connect a DNP master simulator.
   • Map PLC tags to DNP objects.
   • Verify the master can read/write all objects correctly.
   • Test time synchronization.
6. Ethernet Test (if applicable)
   • Connect to a network switch.
   • Assign an IP address.
   • Test DNP over TCP/IP with a master/slave simulator.
   • Verify multiple connections (if supported).
7. Thermal Soak
   • 4 hours at 55 °C in a thermal chamber, running continuous DNP communication.
   • Monitor for any dropped packets or errors.
8. Firmware Verification
   • Read the firmware version via the configuration software.
   • Log it in the test report.
   • If the customer requests a specific version, we verify before shipping.
9. Final QC & Packaging
   • QC sticker with test date and operator initials.
   • Wrap in anti-static bag.
   • Double-box with foam padding.
   • Test report included—serial port test results, DNP protocol logs.

Field Replacement Pitfalls

I’ve swapped these in water plants, oil fields, and power substations. Here’s where people go wrong.

❗Serial Port Wiring
The serial ports are software-configurable for RS232 or RS485. If you wire for RS485 but the module is set to RS232, you’ll get no communication. Check the configuration before you wire.

DNP Addresses
Every DNP device needs a unique address. If you replace a module without setting the correct DNP address, the master won’t find it. The default address is often 1—change it.

Time Sync
DNP slaves need time synchronization for accurate timestamping. If the master doesn’t send time sync, the slave’s timestamps will be wrong. Verify time sync is enabled in both master and slave.

Ethernet vs. Serial
If you have the -104 Ethernet version, you can use both serial and Ethernet simultaneously. But they’re independent—you need to configure both. Don’t assume Ethernet will work just because serial does.

Module Location in Chassis
The module can go in any slot, but some older firmware had issues in slots above a certain number. Check the manual for slot restrictions.

*Nail these five, and your 5136-DNP will talk DNP for years.*

New Original vs. Refurbished: Why It Matters

“New Original (New Surplus)” means this module was manufactured by SST (Woodhead/Molex), packed in its original box, and never installed. The UARTs have zero hours, the serial drivers are unused, and the firmware is as shipped from the factory.

Refurbished risk in plain terms
A refurbished SST module often comes from a decommissioned SCADA system. It may have run for years in a substation or pump station. The serial drivers may have been damaged by lightning surges. A refurbisher tests it at low baud rates and calls it good. At 115k baud, it might fail.

Real cost of a refurbished failure
If this module fails, the SCADA system loses communication with that site. The operator can’t see pump status or change setpoints. If a pump fails and no one knows, you could have a flood or a fire. The cost dwarfs the price difference.

What we provide as proof

• SST box (or photos).
• Serial number recorded.
• Serial port test results (all baud rates).
• DNP protocol logs.
• 12‑month warranty.

Pricing context
We’re priced 35% above the cheapest “pulled” 5136-DNP modules and 20% below SST’s current list price. That pays for the full protocol test, the thermal soak, and the warranty that covers replacement if a UART fails.

Performance Benchmarks & Test Results

Test conditions: ControlLogix test rack, DNP simulator, ambient 24 °C.

We keep the full DNP protocol logs—ask, and we’ll email them.

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