In this paper, we describe how cycle-accurate processor behavior may be efficiently described using Abstract State Machines (ASMs). Given a register transfer description of the target processor, an extraction mechanism is described following the approach in [26] that extracts so called guarded register transfer patterns from the processor description. It will be shown that these may be directly transformed into a set of ASM rules which in turn provide an executable model of the processor for simulation purposes. Here, we use the ASM description language XASM from which the Gem-Mex tool [2] automatically generates a graphical simulator of a given architecture. The feasibility of this approach is demonstrated for an ARM microprocessor.