METHOD AND APPARATUS FOR ADDRESSING A MEMORY CONTAINING DIFFERENT BIT-LENGTH FIELD VARIABLES

A method of accessing a desired memory location applied in a cipher processing apparatus is disclosed. The cipher processing apparatus comprises a plurality of registers and a register storage. The method comprises the steps of: reading a cipher instruction comprising an opcode field and an operand specifier field; reading a base address from one of the plurality of registers according to a register-id sub-field; respectively reading a bit length and an index value from the register storage and an index sub-field; determining the desired memory location according to the base address, the bit length and the index value; and, accessing the desired memory location to obtain a desired field variable. Here, the operand specifier field comprises the register-id sub-field and the index sub-field.