This paper proposes a methodology and a basic structure for the design of wrappers used to adapt cores for use as bus masters. The AMBA AHB protocol is used as a case study in this paper. The first step is to identify the responsibilities of the master. The designer must then develop correspondences between the behaviour of the core and the requirements specified by the protocol. The final step is to build a state machine progressively, adding states to compensate for the core's inability to produce compliant behaviour. An example of a wrapper for the ARM7TDMI is then presented. KEYWORDS Wrapper, bus protocol, AMBA AHB, master, slave, methodology