Rohm LAPIS SEMICONDUCTOR ML620Q503, User Manual

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ML620Q503/Q504 User's Manual
Chapter 2 CPU and Memory Space
FEUL620Q504 2–2
2.2 Program Memory Space
The program memory space stores program codes or vector tables.
The program codes have a length of 16 bits and are specified by a 16-bit program counter (PC).
The program memory space is configured by 32K words (64Kbytes) as one segment (code segment).
The vector table defines the entry address of the program executed at reset and interrupt and is placed in the
segment 0's 0H to 0FEH.
The program memory space capacity determines the memory model. The ML620Q503 and ML620Q504 having
a program memory space of 64Kbytes supports the small model. For details of memory model, see "nX-U16/100
Core Instruction Manual".
Figures 2-1 show the configuration of the program memory space.
CSR:PC
Code segment 0
0:0000H
Vector table
or
Program code
0:00FFH
0:0100H
Program code
0:7BFFH
0:7C00H
Test data
area
(Rewritable)
0:7DFFH
0:7E00H Test data
area
(Not rewritable) 0:7FFFH
8bit
(a) ML620Q503 Configuration of Program Memory Space
Code segment 0
0:0000H
Vector table
or
Program code
0:00FFH
0:0100H
Program code
0:0FBFFH
0:0FC00H
Test data
area
(Rewritable)
0:0FDFFH
0:0FE00H Test data
area
(Not rewritable) 0:0FFFFH
8bit
(b) ML620Q504 Configuration of Program Memory Space
Figure 2-1 Configuration of Program Memory Space
[Note]
• A program code cannot be placed in the test data area (1KB).
When rewriting the content of program memory space, ensure to write "0FFH" in the test data area. If data
in the area is uncertain or other data (i.e. not 0FFH), operating with the code cannot be guaranteed.
• It is recommended that the "0FFH" data (BRK instruction) is set in the unused area of the program memory
space as a fail-safe.