Honeywell MLM Series Modules - MLM-DR16S

Technical Dossier

Product Details And Specifications

Honeywell MLM Series Technical Notes

The Evolution of MLM Architecture

The MLM Series was introduced as a modular successor to Honeywell's earlier fixed-I/O controller platforms, addressing the scalability limitations of monolithic rack designs. Early-generation MLM hardware (circa late 1990s) utilized a parallel backplane bus architecture with a proprietary inter-module communication protocol, supporting scan rates in the 5–50 ms range depending on I/O density. Mid-generation revisions introduced enhanced CPU modules with expanded memory maps and support for Modbus RTU and HART pass-through communication, enabling integration with field instrumentation without gateway hardware.

MLM Full Catalog & Functionalities (SKU List)

CPU & Controller Modules

• MLM-DR16S: 16-point discrete relay output controller module, DIN-rail mount, 24 VDC logic supply
• MLM-CPU01: Base CPU module, 256 KB user program memory, RS-232/RS-485 serial ports
• MLM-CPU02: Enhanced CPU module, 512 KB memory, dual serial + Ethernet 10/100 port
• MLM-CPU03: High-performance CPU, 1 MB memory, redundancy-capable, hot-swap support

Digital Input (DI) Modules

• MLM-DI16A: 16-channel 24 VDC digital input, sink/source configurable, LED status per channel
• MLM-DI32A: 32-channel 24 VDC digital input, high-density, 2-wire field wiring
• MLM-DI16B: 16-channel 120 VAC digital input, optically isolated, DIN-rail mount
• MLM-DI08H: 8-channel HART-enabled digital input with diagnostics pass-through

Digital Output (DO) Modules

• MLM-DO16A: 16-channel 24 VDC transistor output, 0.5 A per channel, short-circuit protected
• MLM-DO16R: 16-channel relay output, Form C contacts, 2 A @ 240 VAC per channel
• MLM-DO08H: 8-channel high-current relay output, 5 A per channel, surge suppression

Analog Input (AI) Modules

• MLM-AI08A: 8-channel analog input, 4–20 mA / 0–10 V selectable, 12-bit resolution
• MLM-AI08H: 8-channel HART analog input, supports HART 5/6/7, field device diagnostics
• MLM-AI16A: 16-channel analog input, 4–20 mA, 13-bit resolution, channel-to-channel isolation

Analog Output (AO) Modules

• MLM-AO04A: 4-channel analog output, 4–20 mA, 12-bit resolution, loop-powered option
• MLM-AO08A: 8-channel analog output, 4–20 mA / 0–10 V, 13-bit, short-circuit protected

Communication & Adapter Modules

• MLM-COMM01: Modbus RTU/ASCII master/slave communication adapter, RS-485, 115.2 kbps
• MLM-COMM02: PROFIBUS DP slave adapter, 12 Mbps, GSD file configurable
• MLM-ETH01: Ethernet TCP/IP communication module, 10/100 Mbps, Modbus TCP support

Power Supply Modules

• MLM-PSU24: 24 VDC rack power supply, 10 A output, 85–264 VAC input, redundancy-capable
• MLM-PSU48: 48 VDC power supply module, 5 A, wide-range AC input, DIN-rail mount

Quality Control for the MLM Range

The MLM Series presents specific quality control challenges due to its backplane bus architecture and the age profile of available surplus inventory. DriveKNMS applies a multi-stage inspection and functional test protocol to all MLM modules prior to dispatch. Visual inspection covers PCB condition, capacitor health, connector pin integrity, and conformal coating status. Functional testing is performed on dedicated MLM rack test benches replicating the original backplane bus electrical environment, verifying correct module enumeration, I/O channel response, and communication protocol handshaking.