25 lines
1.2 KiB
ReStructuredText
25 lines
1.2 KiB
ReStructuredText
.. _harness-clocks:
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Creating Clocks in the Test Harness
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===================================
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Chipyard currently allows the SoC design (everything under ``ChipTop``) to
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have independent clock domains through diplomacy.
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``ChipTop`` clock ports are driven by ``harnessClockInstantiator.requestClock(freq)``.
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``ChipTop`` reset ports are driven by the ``referenceReset()`` function, which is intended to provide an asynchronous reset.
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The ``HarnessBinder`` s in ``ChipTop`` are clocked by the ``HarnessBinderClockFrequencyKey`` value. The reset is provided as a synchronous reset, sync'd to the clock.
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Requests for a harness clock is done by the ``HarnessClockInstantiator`` class in ``generators/chipyard/src/main/scala/harness/HarnessClocks.scala``.
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Then you can request a clock and syncronized reset at a particular frequency by invoking the ``requestClock`` function.
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Take the following example:
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.. literalinclude:: ../../generators/chipyard/src/main/scala/harness/HarnessBinders.scala
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:language: scala
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:start-after: DOC include start: HarnessClockInstantiatorEx
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:end-before: DOC include end: HarnessClockInstantiatorEx
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Here you can see the ``th.harnessClockInstantiator`` is used to request a clock and reset at ``memFreq`` frequency.
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