The Microchip/Datum bc630AT is a half-height XT/AT bus real-time clock module delivering microsecond-precision timekeeping and multi-format time code decoding for synchronization-critical systems. It reads IRIG A, IRIG B, NASA 36, and 2137 time codes, maintains ±10 PPM accuracy during normal operation, and preserves time via battery backup during power loss. The module supports master/slave cascading, external 1PPS and 1/5/10 MHz reference synchronization, event capture with 50 ns minimum pulse detection, and serial time/message communication at 9600 baud. Housed on a half-height card with 16 jumper-selectable interrupt lines (IRQ3–7, 9–12, 14–15), it occupies a single 16-byte block in the PC I/O address space and draws 500 mA at +5VDC.
Technical Specifications
• Time Code Reader: IRIG A (10 kHz ± 2%), IRIG B/NASA 36/2137 (1 kHz ± 2%); modulation ratio 3:1 to 6:1; input 100 mVrms to 1 Vrms at 10 kΩ AC-coupled impedance; flywheel accuracy <3.6 milliseconds per hour with filter enabled
• Real-Time Clock: 24-hour format, ±10 PPM accuracy, microsecond precision, battery-backed time retention
• Synchronization: Master/slave operation; external 1PPS or 1/5/10 MHz reference inputs; TTL/CMOS 1PPS and heartbeat outputs
• Event Capture: TTL/CMOS trigger (positive or negative edge), 50 ns minimum pulse width, 500 µs minimum period
• Serial Interface: 9600 baud, 8 data bits, 1 stop bit, no parity; TX (-) RS-232 compatible
• Power: +5VDC @ 500 mA
• Bus Interface: XT/AT computers; 1 block of 16 bytes; address range 100H–3FFH (AT) or 200H–3FFH (XT); jumper-selectable IRQ lines
– Key Features
• Decodes four standard time code formats in a single module
• Cascadable units via master/slave synchronization
• Sub-microsecond timing for event logging and system coordination
• Flywheel operation preserves time accuracy during signal loss
• TTL/CMOS logic-level I/O for direct integration with test and measurement systems
– Typical Applications
• High-precision data acquisition and event timestamping
• Synchronized multi-instrument test benches
• IRIG time code distribution in legacy and hybrid systems
• Laboratory timing references with external atomic clock sync
– Compatibility & Integration
The bc630AT occupies half-height form factor in XT/AT bus slots. Sixteen 8-bit control registers manage all timing, synchronization, and output functions. Interrupt routing via jumpers eliminates address conflicts in crowded I/O environments.
