Timecode Reader/Generator with ISA Interface
- IRIG-A, IRIG-B, NASA36 timecode reader
- IRIG-B timecode generator
- IRIG-B output
- Optional GPS synchronization
- Freewheel capability
- Time-tag input
- Programmable start/stop time output and interrupt capability
Product Overview
The Spectracom Model TPRO-PC performs timing and synchronization functions referenced to an input timecode signal. The board synchronizes its on-board clock to the incoming timecode. The on-board clock’s time is also provided as an IRIG-B output. Other features include a time-tag TTL input, a programmable “heartbeat” pulse or squarewave output (with interrupt capability), and a programmable “match” start/stop time output (with interrupt capability).
The board continues to increment time (“freewheel”) in the absence of an input timecode. Thus, the board can be used as an IRIG-B timecode generator by setting the initial time via the ISA bus.
The input timecode format (IRIG-B, IRIG-A or NASA36) is automatically detected. Synchronization to the input timecode is also automatic and can be enabled/disabled via the ISA bus. A propagation delay offset may be specified to compensate for cable delays.
The timecode input is an amplitude modulated sine wave. An automatic gain control (AGC) circuit permits a wide range of input amplitudes. The timecode input is differential; the board does not reference this signal to ground. A single-ended input (referenced to ground) is also acceptable.
The board can be ordered with option “-01” to synchronize to a one-pulse-per-second (1 PPS) input instead of an incoming timecode. In this case, the initial time is programmed via the ISA bus, and the board begins counting on the next 1 PPS pulse.
ISA Interface
The board occupies 16 consecutive addresses in I/O (not memory) space. Jumpers on the board allow for selection of base address. There is also a jumper to select the interrupt level. All board functions can be used without interrupts, if desired.
All board functions can be accessed using 8-bit transfers. Additionally, the time can be read with four 16-bit transfers. Binary-coded decimal (BCD) format is used for setting and reading the time.