The Microchip/Datum bc620AT is a PC-based time and frequency module that delivers precision synchronization to host computers and peripheral data acquisition systems. It integrates via ISA/EISA expansion slot and accepts external time references—GPS or IRIG time code signals—to discipline a 10 MHz oscillator with 100 nanosecond clock resolution. The module decodes IRIG A, IRIG B, NASA 36, and 2137 time code formats at carrier frequencies of 10 kHz ± 2% (IRIG A) or 1 kHz ± 2% (IRIG B, NASA 36, 2137), with input impedance of 10 kΩ AC coupled and modulation ratios from 3:1 to 6:1. Input amplitude ranges from 100 mVrms to 1 Vrms.
Technical Specifications
Internal Oscillator & Clock
• Disciplined 10 MHz oscillator
• 100 nanosecond clock resolution
• Temperature-Compensated Crystal Oscillator (TCXO) option
• Ovenized crystal oscillator option
• Battery-backed clock for power-loss operation at 10 PPM accuracy
Time Code Input
• Supported formats: IRIG A, IRIG B, NASA 36, 2137
• IRIG A carrier: 10 kHz ± 2%
• IRIG B/NASA 36/2137 carrier: 1 kHz ± 2%
• Input impedance: 10 kΩ (AC coupled)
• Modulation ratio: 3:1 to 6:1
• Input amplitude: 100 mVrms to 1 Vrms
Signal Outputs
• IRIG B time code output (synchronized to input source)
• Frequency outputs: 1, 5, or 10 MHz
• 1 Pulse Per Second (1PPS): TTL/CMOS, positive edge
• Heartbeat pulse output: TTL/CMOS, positive edge
• Programmable pulse rate outputs/interrupts
• Programmable time strobe output/interrupt
Signal Inputs
• External event capture: TTL/CMOS trigger, positive or negative edge, 50 ns minimum width, 500 µs minimum period
• External oscillator input: 10 MHz reference
• 1 PPS input for synchronization
Timekeeping
• Flywheel capability maintains time accuracy when external source is lost
• Battery-backed operation during power interruption
– Key Features
• High-speed time requests with zero-latency bus access
• Multi-format time code generation and translation
• External event time-stamping capability
• Disciplined oscillator maintains frequency accuracy during source loss
