The thorny issues of avoiding the noisy environment of a PC and its unstable PCI clock whilst still allowing a PC to be synchronised to an external timebase may perhaps be adressed by:
Producing a simple PCI (or PCIe, or even ISA bus card - still widely used in industry) board that has a counter clocked by the PCI clock together with suitable registers used to time tag PCI bus reads etc as required by the PC software. If the counter rollover occurs at an approximately 1Hz rate then an optical (or equivalent isolation technique) can be used to produce an output isolated from the PC which can be used by an external multichannel high resolution time tagging instrument to time tag the counter rollover with a stable low noise timebase. This avoids compromising the high the performance of the resolution time tag instrument with the high noise PC environment and its relatively unstable PCI bus clock whilst still allowing the PC to be synchronised to a stable and accurate external timebase. With such a simple board plugged into the PCI (or PCIe , ISA) bus it should be easy and relatively inexpensive to produce a new one when moving to PCIe or its successors. The same external timestamping instrument can then be retained for years as PC buses come and go. The potential issue of obsolete communication standards is best addressed by using a separate board to implement the interface (LAN, USB, RS232 etc) which can be updated if and when required. Optical (serial port) or transformer (LAN) isolation can be used to isolate the timetag device from the noisy PC ground system whilst permitting communication between the PC and the instrument. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
