Patent ID: 6978358
Filing Date: 2005-12-20
Classification: G06F

Abstract:
1. A data processing apparatus for executing stack-based instructions specifying operations to be executed upon stack data items held in a stack, a first type of stack data item having a first size, and a second type of stack data item having a second size, the data processing apparatus comprising: a register bank containing a plurality of ‘n’ bit registers for storing data items, a set of registers within said register bank being allocatable to hold stack data items from a portion of the stack, each register in said set being able to store as an ‘n’ bit value a stack data item of said first type or a stack data item of said second type; an arithmetic logic unit for executing operations upon the data items held in said registers; a decoder for decoding a stack-based instruction to specify a number of operations to be executed by the arithmetic logic unit upon one or more stack data items held in predetermined registers in said set; a stack controller for controlling the movement of the stack data items between the stack and the set of registers, and responsive to the decoder to cause the one or more stack data items to be held in the predetermined registers; the stack controller being arranged to cause an indication of the size of each stack data item held in the registers within said set to be maintained, such that when one of those stack data items is moved from the set of registers to the stack, the stack controller can cause that stack data item to be stored on the stack at the size defined by its type.