Flash Memory Emulation By Ram - Renesas H8/3067 Series User Manual

18.7

Flash Memory Emulation by RAM

Erasing and programming the flash memory takes time, which can make it difficult to tune
parameters and other data in real time. In this case, overlapping part (H'FFF000 to H'FFF3FF) of
RAM onto a small block area of flash memory can be performed to emulate real-time
reprogramming of flash memory. This RAM reassignment is performed using bits 3 to 1 in the
RAM control register (RAMCR).
After the RAM area change, two areas can be accessed: the overlapped flash memory area and the
original RAM area (H'FFF000 to H'FFF3FF). For a description of the RAMCR and RAM area
setting procedure, see section 18.3.3 RAM Control Register (RAMCR).
Example of real-time emulation of flash memory
An example of RAM area H'FFF000 to H'FFF3FF overlapping EB2 (H'000800 to H'000BFF)
flash memory area is shown below.
H'000000
Block area
H'000800
EB2
area
H'000BFF
H'000FFF
Figure 18.14 Example of RAM Overlapping Operation
Flash memory
space
Overlapping RAM
(Image RAM area)
*
H'FFEF20
On-chip
RAM area
H'FFEFFF
H'FFF000
(Real RAM area)
H'FFF3FF
H'FFF400
H'FFFF1F
<Procedure>
1 Part (H'FFF000 to H'FFF3FF) of RAM
overlaps the area (EB2) needed to carry out
real-time reprogramming.
(Bits 3 to 1 in the RAMCR are set to 1, 1, 0
and the overlap flash memory area (EB2)
is selected.)
Real-time reprogramming is carried out using
2
the overlapping RAM.
After the reprogramming data is verified, RAM
3
overlapping is released. (RAMS bits are cleared.)
The data written to H'FFF000 to H'FFF3FF in RAM
4
are written to flash memory space.
Note:
When part (H'FFF000 to H'FFF3FF) of RAM
*
overlapped a small block area of flash
memory, the overlapped flash memory
area cannot be accessed. This area can
be accessed by releasing overlapping.
Rev. 4.00 Jan 26, 2006 page 643 of 938
Section 18 ROM
REJ09B0276-0400