Rohm LAPIS SEMICONDUCTOR ML620Q503, User Manual

Page: 502 / 553

ML620Q503/Q504 User's Manual
Chapter 27 Flash Memory Control
FEUL620Q504 27- 13
27.3.5 Boot Area Remap Function by Hardware
When the power-on reset by power-on or the reset by the RESET_N pin is released under the condition that the
external pin (TEST0) is set to High, 512 bytes of ISP boot area
*
and 512 bytes of test area (1 KB in total) are
remapped to 0:0000H to 0:03FFH to allow the boot by the program in the ISP boot area. The ISP boot area is
also remapped to 0:0400H to 0:0FFF repeatedly.
By writing the boot program in the ISP boot area in advance, the following functions can be achieved:

When startup cannot be performed due to power down while rewriting the block 0 (area of 16 KB from
0000H) of FLASH, where the boot program is normally placed, startup (boot) from the ISP boot area can
avoid a situation that recovery is not possible.

The boot program can rewrite the internal program of the LSI by using UART which provides external
communication. This can achieve a function equivalent to Flash Writer.
*: The ISP boot area differs among products. (0:FC00H to 0:FDFFH for ML620Q504).
Figure 27-4 shows the memory map before and after remapping.
Figure 27-4 Boot Switch by Setting External Pin (TEST0)
0:0000H
Normal boot area
Test area
(Read-only)
0:FC00H
0:FE00H
0:0000H
Program area
Program area
Normal boot (TEST0 pin = L) before remapping ISP boot (TEST0 pin = H) after remapping
Remapping
0:1000H
Test area
(Writable)
Test area
(Read-only)
0:FC00H
0:FE00H
ISP boot area
Test area
(Read-only)
ISP boot area
Test area
(Read-only)
ISP boot area
Test area
(Read-only)
ISP boot area
Test area
(Read-only)
ISP boot area
0:1000H
0:0400H
0:0800H
0:0C00H