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On-Chip RAM Area Divisions in Boot Mode: In boot mode, the RAM area is divided into an
area used by the boot program and an area to which the user program is transferred via the SCI, as
shown in figure 18.8. The boot program area can be used when a transition is made to the
execution state for the user program transferred to RAM.
Note : * The boot program area cannot be used until a transition is made to the execution state
for the user program transferred to RAM. Note also that the boot program remains in
this RAM area even after control branches to the user program.
Notes on using the boot mode
(1) When this LSI comes out of reset in boot mode, it measures the low period the input at the
SCI's RXD
pin. The reset should end with RXD
1
states for this LSI to get ready to measure the low period of the RXD
(2) If any data has been written to the flash memory (if all data is not H'FF), all flash memory
blocks are erased when this mode is executed. Therefore, boot mode should be used for initial
on-board programming, or for forced recovery if the program to be activated in user program
mode is accidentally erased and user program mode cannot be executed, for example.
(3) Interrupts cannot be used during programming or erasing of flash memory.
(4) The RXD
and TXD
1
H'FFEF20
H'FFF3FF
H'FFF400
H'FFFF1F
Figure 18.8 RAM Areas in Boot Mode
pins should be pulled up on the board.
1
Boot program
area *
User program
transfer area
high. After the reset ends, it takes about 100
1
Rev. 4.00 Jan 26, 2006 page 627 of 938
Section 18 ROM
input.
1
REJ09B0276-0400
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