HD64F3039F18 Datasheet, PDF (498/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 15 ROM
15.7 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'FF800 to H'FFBFF) 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'FF800 to H'FFBFF). For a description of the RAMCR and RAM area
setting procedure, see section 15.3.3, RAM Control Register (RAMCR).
Example of real-time emulation of flash memory
An example of RAM area H'FF800 to H'FFBFF overlapping EB2 (H'00800 to H'00BFF) flash
memory area is shown below.
H'00000
Block area
Flash memory
space
Procedure:
1. Part (H'FF800 to H'FFBFF) 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.)
EB2 H'00800
area _H'00BFF
H'00FFF
Overlapping RAM
*
(Image RAM area)
H'FEF10
On-chip
RAM area
H'FF800
H'FFBFF
H'FFC00
H'FFF0F
(Real RAM area)
2. Real-time reprogramming is carried out using
the overlapping RAM.
3. After the reprogramming data is verified, RAM
overlapping is released. (RAMS bits are cleared.)
4. The data written to H'FF800 to H'FFBFF in RAM
are written to flash memory space.
Note: * When part (H'FF800 to H'FFBFF) 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.
Figure 15.14 Example of RAM Overlapping Operation
Rev.3.00 Mar. 26, 2007 Page 474 of 682
REJ09B0353-0300