Rohm LAPIS SEMICONDUCTOR ML620Q503, User Manual

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ML620Q503/Q504 User's Manual
Chapter 27 Flash Memory Control
FEUL620Q504 27- 12
27.3.4 Boot Area Remap Function by Software
This function can remap the area from 0000H to 0FFFH (4 KB) to the area of the same size (4 KB) starting from
the address set in the REMAPADD register.
The program can start from the remapped area by setting the start address of the area to remap in the
REMAPADD register and performing the software reset (* only CPU is reset) by execution of the BRK
instruction. For the BRK instruction, refer to "nX-U16/100 Core Instruction Manual".
The remap function also remaps the vector table areas (reset vector area, hardware interrupt vector area, and
software interrupt vector area). It is feasible to manage interrupts independently by the program in the remap area.
If the program size is 4 KB or less, it is feasible to develop the program independently of the main program. This
is suitable for the cases that want to control interrupts such as the self-rewrite program separately from the normal
interrupt.
Figure 27-2 shows a sample program for remap (when the start address of the remap area is F000H). Figure 27-3
shows the memory map before and after remapping.
MOV R0, #00FH ;
ST R0, 0F0ECH ; Set the higher 4 bits of the start address of the area
; to remap to the REMAPADD register (0F0ECH).
MOV PSW, #02H ; Set the interrupt level (ELEVEL) to 2.
BRK ; Execute the BRK instruction.
; Execution starts with the code at the remapped F000H.
Figure 27-2 Sample Program for Remap
Figure 27-3 Memory Map before/after Remapping
[Note]
If the area 0:0000H to 0:1000H (4KB) before remapping need to be read after remapping, read it from 8th
segment. If the area 0:0000H to 0:1000H (4KB) before remapping need to be written, set the address
(0:0000H to 0:1000H) that was used before remapping to the flash address register (FLASHA). For FLASHA,
refer to "27.2.2 Flash Address Register (FLASHA)".
0:0000H
Normal boot area
4KB
Test area
Program area
0:FC00H
0:0000H
Program area
Before remapping After remapping
0:F000H
Program area
Remap
0:1000H 0:1000H
Test area* 1 KB
Program area
3KB
0:FC00H
0:F000H
Test area 1 KB
Program area
3KB
* The test area cannot be used as program area.