MC81F420444 April 24, 2012 Ver.1.419. MEMORY ORGANIZATIONThis MCU has separated address spaces for the *program memory* and the *data Memory*.The program memory is a ROM which stores a program code. It is not possible to write a data at theprogram memory while the MCU is running.The Data Memory is a REM which is used by MCU at running time.9.1 RegistersThere are few registers which are used for MCU operating.Accumulator( A Register ) : Accumulator is the 8-bit general purpose register, which is used foraccumulating and some data operations such as transfer, temporary saving, and conditionaljudgment , etc.And it can be used as a part of 16-bit register with Y Register as shown below.X, Y Registers: In the addressing mode, these are used as a index register. It makes it possible toaccess at Xth or Yth memory from specific address. It is extremely effective for referencing asubroutine table and a memory table.Figure 9-1 Configuration of RegistersFigure 9-2 Configuration of YA 16-bit Registers
