The Microchip/Datum bc637VME is a 6U single-width VME module that provides precision timing and frequency synchronization using GPS satellite signals or external time code inputs. The module delivers zero-latency time access across the VMEbus with 100 nanosecond resolution, paired with a disciplined 10 MHz oscillator. It generates synchronized IRIG B and IRIG H time code outputs, decodes multiple time code formats (IRIG B, 2137, XR3), and captures event time stamps on external TTL pulses with microsecond-level precision. Five maskable interrupt sources support programmable pulse generation, epoch outputs, and time-coincidence strobes across VMEbus IRQ levels 1–7.
Technical Specifications
• Form Factor: 6U, single-width VME module
• Time Sources: GPS satellites (receiver and antenna included) or time code signals (IRIG B typical)
• Disciplined Oscillator: 10 MHz
• Clock Resolution: 100 nanoseconds
• Time Access Latency: Zero across VMEbus (days to 100 nanoseconds)
• Flywheel Operation: Maintains time during loss of synchronization source
• Battery-Backed Clock: +/− 10 PPM holdover when main power lost
• Time Code Generation: IRIG B (modulated and DC level shift) and IRIG H, synchronized to input source
• Time Code Decoding: IRIG B, 2137, XR3 formats; carrier range ±50 ppm; modulation ratio 3:1 to 6:1; input amplitude 0.5–5 V peak-to-peak; 10 kΩ AC-coupled impedance
• Frequency Outputs: TTL levels at 1 MHz, 5 MHz, or 10 MHz (programmable); custom rates via formula 10,000,000 / (n1 × n2) where 1 < n1, n2 < 65536
• Event Time Capture: Days through 0.1 microsecond resolution; positive or negative edge trigger; bus interrupt generation supported
• Programmable Outputs: Periodic pulse/interrupt rates; strobe at predetermined time; time coincidence strobes (hours to milliseconds); one-second epoch output
• Interrupt Control: Five maskable sources; IRQ levels 1–7 programmable
• Front Panel: LED display (hours, minutes, seconds)
• VMEbus Interface: 32 D16 registers; A16:D16 transfers; 64-byte boundary addressing
• VXI Compatibility: Selectable via DIP switch
– Key Features
• GPS receiver and antenna integrated
• Simultaneous time code format generation and decoding
• Sub-microsecond event logging on external triggers
• Maintains timing during GPS loss and power failure
• Programmable output frequencies with flexible rate calculation
• Multiple interrupt masking and IRQ routing options
– Typical Applications
Precision event logging, network time synchronization, frequency distribution in test environments, time-tagged signal acquisition, and systems requiring holdover performance during signal loss.
– Compatibility & Integration
Standard VMEbus D16 register interface; VXI-compatible with switch selection. Accepts IRIG time code from external sources or operates autonomously with onboard GPS.
