ARM Technical Support Knowledge Articles

How to the Fast Models handle active low ports on the cores?

Applies to: Fast Models

Answer

Ports in Fast Model implement a given protocol which defines the behaviours that the port implements/uses. Depending on the protocol used, the activeness of the hardware signal could be handled differently.

Signal Protocol

The signal protocol, which is used for example for the fiq and irq ports on most cores, implements two behaviours:

• sg::Signal::Set
• sg::Signal::Clear

This protocol does not refer to the level of the signal but instead the intention, making the protocol level independent. Care must be taken when converting from a level sensitive protocol to a level independent one to ensure the correct meaning is preserved. Please note that this meaning will be different between active high and active low protocols

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