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use LEMO 00 connectors**
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use LEMO 00 connectors**
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[Bottom view](https://www.ohwr.org/465)
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[Bottom view](https://www.ohwr.org/465)
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## Functional system specifications
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## [Functional system specifications](FmcDelFuncSpec)
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- 1 ns resolution or better.
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- Accuracy: */- (500 ps* timebase accuracy).
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- Timebase accuracy: +/- 4ppm.
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- Implementation details: timebase from a local TCXO on FMC card
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and needs calibration. The 4ppm accuracy is the one of the
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on-board TCXO. Much better accuracy will be reached when used on
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a White Rabbit enabled FMC carrier.
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- 500 ns - 120 s range or better.
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- 1 input, selectable between front panel and FMC connector. This
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input is shared by all output channels.
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- Input electrical standard will be TTL (not LVTTL), with optional 50
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Ohm termination. The default power-up state is high impedance. A LED
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will signal termination status.
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- External input needs to be protected against +15V pulses with a
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pulse width of at least 10us @ 50Hz (with protection diodes if
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possible).
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- Need to withstand a continuous short-circuit on all the outputs at
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the same time.
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- Output standard: 50 Ohm TTL drivers (with 2V/ns or faster rising
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edges). At power-up the default output state is low, with no
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glitches.
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- LEMO 00 connectors for input and outputs.
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- 4 individually controllable outputs, with independent delay, width
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and enable/disable.
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- Delay circuit reacts on input rising edge. Minimum input pulse
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width: 100 ns. Pulses shorter than 20ns should be ignored.
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- Input pulses will be ignored until the longest programmed delay of
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the previous input pulse has expired.
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- Output pulse width is programmable in steps of system clock ticks
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(~125 MHz) with a 16-bit register per output channel.
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- Jitter will be measured by probing two output channels which have
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been programmed with the same delay. The sigma of the distribution
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of delay measurements between the rising edges of any two channels
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should not exceed 100 ps. This should hold for any programmed delay
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within the whole delay range.
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- A circular buffer will contain time tags for at least the last 100
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input and output pulses. These time tags will at first be rough UTC
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(counter initialized by SW) giving ~ms accuracy. Later, with a
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WR-enabled solution, they can be much more accurate.
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- Uses FMC Low pin count (LPC) connector.
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-----
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-----
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