The Microchip/Datum bc635VME is a single-width VMEbus Time and Frequency Processor that delivers precise timing and frequency references to host computers and data acquisition systems. It acquires time from GPS satellites or external time code signals—primarily IRIG B—and maintains synchronization through a disciplined 10 MHz oscillator with a 100 nanosecond clock. When the reference source is lost, flywheel operation preserves timing at the last known rate, while a +/-10 PPM battery-backed clock ensures continuity during power loss.
Technical Specifications
Oscillator & Timing
• Disciplined 10 MHz oscillator with 100 nanosecond clock
• Battery-backed clock: +/-10 PPM accuracy
• Flywheel operation maintains last known reference rate
Input Interfaces
• Time code decoding: IRIG B, 2137, XR3 (0.5 to 5 V peak-to-peak, AC-coupled, 10 kΩ impedance)
• IRIG A support: 10 kΩ DC-coupled
• Carrier tolerance: +/- 50 ppm
• External 10 MHz input: TTL/CMOS, 45% to 55% duty cycle, 1.5 to 4 V peak-to-peak, AC-coupled, 2.5 kΩ impedance
• Event capture: TTL/CMOS, positive or negative edge triggered
• 1 PPS input: TTL/CMOS positive edge synchronized to time
Output Interfaces
• Time code generation: IRIG B (modulated and DC level shift), IRIG H (DC level shift)
• Frequency outputs: 10 MHz, 5 MHz, 1 MHz (80/20 duty cycle) TTL/CMOS square waves
• Programmable frequency outputs: 10,000,000 / (n1 × n2) where 1 < n1 < 65536, 1 < n2 < 65536
• 1 PPS output: 200 ms positive pulse into 50 Ω
• Programmable time strobe: Configurable from hours to milliseconds, plus each-second mode
• Interrupt outputs: Five maskable sources, IRQ levels 1–7 programmable
– Key Features
• VMEbus single-width module (6U × 160 mm)
• 32 D16 register block for VMEbus control and access
• Supports GPS and multiple time code formats
• Event timestamping with TTL/CMOS edge detection
– Typical Applications
• Telecommunications synchronization
• Data acquisition systems requiring high-accuracy timing
• Control systems with precise frequency references
– Compatibility & Integration
Operates as a VMEbus slave module with block-accessible D16 registers via standard VMEbus protocol.
