1. A processing device for executing virtual machine instructions; the processing device comprising: an instruction memory for storing instructions including at least one of the virtual machine instructions; a microcontroller comprising a processor comprising a predetermined microcontroller core for executing native instructions from a predetermined set of microcontroller specific instructions; the native instructions being different from the virtual machine instructions; and a pre-processor comprising: a converter for converting at least one virtual machine instruction, fetched from the instruction memory into at least one native instruction; and feeding means for feeding native instructions to the microcontroller core for execution; characterised in that: the processor is of a type which after the occurrence of a predetermined condition, such as an interrupt, requests re-feeding of up to a predetermined maximum of n native instructions, where n>1; and the feeding means comprises means for in response to the processor requesting re-feeding of a number of native instructions, re-feeding the requested native instructions.