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The following rules apply to unconnected input ports on primitive, megafunction, and macrofunction symbols and instances.
Unused inputs to flipflop primitives have the following defaults:
CLRN: |
VCC (inactive) |
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PRN: |
VCC (inactive) |
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ENA: |
VCC (active) |
The data and clock inputs to flipflops and the data and ENA inputs to latches are required.
An unused OE input to a TRI buffer defaults to VCC (active, output enabled).
Unused inputs to logic primitives in Block Editor files must be connected to VCC or GND.
The default logic levels for unused inputs to megafunctions, if any, are documented in the Help for each megafunction. There may not be a default input to some ports on megafunctions, and failure to connect such ports will cause the Compiler to issue error messages.
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- PLDWorld - |
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