Motorola MVME374-1 VMEbus Intelligent Offload Ethernet Communications Coprocessor (68K Legacy DCS Gateway Card)

Manufacturer Background: Motorola Computer Group → Freescale → Emerson Embedded Computing; Fully EOL obsolete, no new factory production; only refurbished/tested spare units available for legacy VME DCS systems

Part Number: MVME374 (Main variant MVME374-1)

Product Type: 6U single-height VMEbus dedicated intelligent Ethernet coprocessor; not a general main CPU; offloads full TCP/IP stack from host VME controller to guarantee real-time closed-loop control performance

Matching Platform: VME Rev C backplane A16/A24/A32, D16/D32 master/slave; compatible with Foxboro I/A Series, old Emerson Ovation VME racks, aerospace ground test, thermal power plant safety interlock systems

Core Hardware Overview: 1. CPU: MC68020 32-bit CISC @16MHz / 25MHz; optional MC68881/MC68882 floating-point coprocessor for complex calculation tasks 2. Shared Buffer RAM: Base 1MB DRAM, expandable to 4MB / 8MB for network packet buffering 3. Network: 1×15-pin AUI 10Mbps 10BASE5 Ethernet (coax / external twisted-pair transceiver) 4. Local I/O: Dual RS232/RS422 UART serial ports, IEEE1284 parallel printer port 5. VME Interface: Full master/slave DMA engine, supports all 7 VME interrupt priority levels 6. Front Panel: Run LED, Fault LED, Reset pushbutton, Abort emergency stop button 7. Power: Powered entirely via VME backplane +5V DC, typical consumption 1.5A 8. Software: MOTLoad/MVMEBUG firmware, built-in full TCP/IP stack; supports VxWorks, pSOS, OS-9 RTOS 9. Mechanical: Standard 6U single-height Eurocard, NO RTM rear transition module (all I/O front-panel only)

1. Product Overview

MVME374 is an early-generation dedicated communication coprocessor for VMEbus systems, fundamentally different from general-purpose PowerPC SBCs like MVME3100. Its exclusive design purpose is to independently process all Ethernet TCP/IP traffic, completely offloading network packet parsing, routing and protocol stack work from the main VME control CPU. By separating network workload from critical closed-loop control, SOE event timestamp and safety ESD interlock logic, it eliminates network congestion latency risks that could cause control failure. It uses independent MC68020 processor and dedicated shared memory buffer to isolate LAN traffic from real-time process control data on the VME backplane. Equipped with classic AUI 10Mbps thick-coax Ethernet interface, it was widely deployed in 1990s–2000s legacy power plant Foxboro I/A and Ovation VME DCS racks as dedicated HMI gateway, SOE data upload and field instrument data aggregation board. Conformal coated PCB versions meet ISA G3 anti-salt/humidity standards for offshore Zone2 hazardous control rooms, operating 0℃~+70℃ standard, -40℃~+70℃ ruggedized coated variant. Motorola ceased mass production decades ago; all available stock is surplus used or fully refurbished tested spare parts for aging VME cabinet renovation and channel expansion projects.

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