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manual: precisions about TTL sampling

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Sebastien Bourdeauducq 2016-12-03 11:24:40 +08:00
parent 617f6897a4
commit 35200387b5
1 changed files with 5 additions and 3 deletions
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doc/manual/rtio.rst
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@ -133,6 +133,8 @@ The :meth:`artiq.coredevice.ttl.TTLInOut.count` method of an input channel can l
The :meth:`artiq.coredevice.ttl.TTLInOut.gate_rising` method leaves the timeline cursor at the closure time of the gate and ``count()`` must necessarily wait until the gate closing event has actually been executed which is sometime with ``rtio_counter > now``. The :meth:`artiq.coredevice.ttl.TTLInOut.gate_rising` method leaves the timeline cursor at the closure time of the gate and ``count()`` must necessarily wait until the gate closing event has actually been executed which is sometime with ``rtio_counter > now``.
In these situations where ``count()`` leads to a synchronization of timeline cursor and wall clock, a ``delay()`` is necessary to reestablish positive slack so that output events can be placed. In these situations where ``count()`` leads to a synchronization of timeline cursor and wall clock, a ``delay()`` is necessary to reestablish positive slack so that output events can be placed.
Similar situations arise with methods such as :meth:`artiq.coredevice.ttl.TTLInOut.sample_get` and :meth:`artiq.coredevice.ttl.TTLInOut.watch_done`.
.. wavedrom:: .. wavedrom::
{ {
signal: [ signal: [
@ -151,10 +153,10 @@ In these situations where ``count()`` leads to a synchronization of timeline cur
Overflow exceptions Overflow exceptions
------------------- -------------------
The RTIO input channels buffer input events received while an input gate is open. The RTIO input channels buffer input events received while an input gate is open, or at certain points in time when using the sampling API (:meth:`artiq.coredevice.ttl.TTLInOut.sample_input`).
The events are kept in a FIFO until the CPU reads them out via ``count()`` (or :meth:`artiq.coredevice.ttl.TTLInOut.timestamp_mu`). The events are kept in a FIFO until the CPU reads them out via e.g. :meth:`artiq.coredevice.ttl.TTLInOut.count`, :meth:`artiq.coredevice.ttl.TTLInOut.timestamp_mu` or :meth:`artiq.coredevice.ttl.TTLInOut.sample_get`.
If the FIFO is full and another event is coming in, this causes an overflow condition. If the FIFO is full and another event is coming in, this causes an overflow condition.
The condition is converted into an :class:`artiq.coredevice.exceptions.RTIOOverflow` exception that is raised on a subsequent invocation of one of the readout methods (``count()`` or ``timestamp_mu()``). The condition is converted into an :class:`artiq.coredevice.exceptions.RTIOOverflow` exception that is raised on a subsequent invocation of one of the readout methods (e.g. ``count()``, ``timestamp_mu()``, ``sample_get()``).
Seamless handover Seamless handover
----------------- -----------------