The Microchip/Datum bc635VME-C is a VME-based Time and Frequency Processor that delivers disciplined timing and frequency references for host computers and data acquisition systems requiring precise synchronization. The module acquires time from external IRIG B time code signals, maintains a rate-matched 10 MHz oscillator, and outputs a 100 nanosecond clock for zero-latency time access across the VMEbus down to 100 nanosecond resolution.
Technical Specifications
Timing & Frequency:
• Disciplined 10 MHz oscillator, rate-matched to external time source
• 100 nanosecond resolution clock
• Programmable frequency outputs: 1 MHz, 5 MHz, and 10 MHz (TTL)
• Programmable periodic output: 10,000,000 / (n1 × n2) Hz, where 1 < n1 < 65536 and 1 < n2 < 65536
• Battery-backed clock maintains ±10 PPM accuracy during source loss
Time Code I/O:
• Input: Decodes IRIG B, 2137, and XR3 time codes; optional IRIG A and NASA 36
• Output: IRIG B (AM modulated and DC level shift formats simultaneously) and IRIG H
• Front-panel LED display: hours, minutes, and seconds
Event Handling & Interrupts:
• External event capture with time latch (TTL/CMOS input, ±edge selectable, 20 nanosecond minimum pulse width, 250 nanosecond minimum period)
• 1PPS input/output support; 1PPS output is TTL/CMOS positive edge, 200 ms pulse into 50 Ω
• Programmable periodic pulse generation or interrupt
• Time-coincidence strobe: programmable from hours to milliseconds, plus "each second" mode
• Five maskable interrupt sources (external event, periodic output, time strobe, 1PPS epoch, output data packet); IRQ levels 1–7 programmable
– Key Features
• Zero-latency time-on-demand access across VMEbus
• Flywheel capability maintains time during external source loss
• TTL/CMOS compatible I/O
• Multiple time code format support for flexible system integration
– Compatibility & Integration
VME form factor for direct integration into existing VME-based instrumentation and control systems. Supports standard VMEbus protocols for time distribution and synchronization applications.
