The Curtiss-Wright/Pentland Systems MPV991 is a 6U VMEbus timer/counter board that delivers ten configurable 16-bit channels for precision timing and counting applications. Built on two Am9513A System Timing Controllers, the board supports BCD or binary counting modes with programmable up/down direction control. Each channel can source from four internal frequency derivatives of a 4 MHz clock or from four external pins per STC, with selectable input polarity and Schmitt-trigger conditioning. Hardware and software gating enables each gate input to control up to three counters simultaneously, while counter outputs route through an AM9519A Universal Interrupt Controller for VME Priority Interrupt Bus capability. The architecture supports counter concatenation up to 80 bits, quadrature detection, eight digital inputs, eight gate inputs, and eight tri-state outputs.
## Technical Specifications
• VMEbus Specification Rev. C.1 compliance
• Single 6U Eurocard form factor
• Two Am9513A System Timing Controllers (STCA, STCB)
• Ten 16-bit general-purpose timer/counter channels
• Internal clock: 4 MHz
• Four internal frequency sources per counter
• Four external input pins per STC
• Programmable count modes: BCD or binary
• Programmable count direction: up or down
• Input polarity: active HIGH or active LOW selectable
• Schmitt-trigger inputs with optional low-pass filtering
• Hardware and software gating per counter
• Gate inputs: eight total (three counters controllable per gate)
• Output modes: pulse or toggled
• Output interface: software-enabled tri-state buffer
• Interrupt control: AM9519A Universal Interrupt Controller
• Maximum counter concatenation: 80 bits
• Quadrature detection circuitry included
• Digital input channels: eight
• Tri-state output channels: eight
• External connectivity: two 37-way D-type connectors (P3 for STCA, P4 for STCB) or backplane P2 connector
• Interface variants: standard (74LS14 Schmitt-trigger inverters) or differential (MPV991D with 100 Ω, 1/2W terminated receivers)
## Key Features
• Non-disruptive counter read capability—accumulated counts accessible without halting operation
• Differential receiver option (MPV991D) for noise-sensitive or remote installations
• Flexible input selection from onboard or external sources
• VME Priority Interrupt Bus integration via UIC
## Typical Applications
Precision timing and event counting in VMEbus instrumentation, real-time data acquisition systems, and industrial control environments requiring multi-channel synchronization.
## Compatibility & Integration
Full VMEbus Specification Rev. C.1 compliance ensures compatibility with standard VME backplanes and peripheral modules. Front-panel and backplane connector options accommodate diverse system architectures.
