Some of the resources only require signals from AHB or control registers to generate output, and are called primary resources. Other resources require outputs from other resources, and are called derived resources. To simplify the design, all resource outputs are connected to an internal event bus. Derived resources operate on the signal values on this internal event bus, and various resource control registers in the register blocks.

Derived resources operate on a Boolean function of two different resources in the internal event bus. This is typically specified by a 17-bit register. The encoding of the event and resources is described in HTM derived resources.