Curtiss-Wright / Pentland Systems MPV991 VME Bus Timer / Counter Board

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.