Figure 19.14 Example Of Ram Overlap Operation - Hitachi H8/3062 Hardware Manual

19.8 Flash Memory Emulation in RAM
As flash memory programming and erasing takes time, it may be difficult to carry out tuning by
writing parameters and other data in real time. In this case, real-time programming of flash
memory can be emulated by overlapping part of RAM (H'FFF000–H'FFF3FF) onto a small block
area in flash memory. This RAM area change is executed by means of bits 3 to 1 in the RAM
control register (RAMCR). After the RAM area change, access is possible both from the area
overlapped onto flash memory and from the original area (H'FFF000–H'FFF3FF). For details of
RAMCR and the RAM area setting method, see section 19.3.4, RAM Control Register (RAMCR).
Example of Emulation of Real-Time Flash Memory Programming: In the following example,
RAM area H'FFF000–H'FFF3FF is overlapped onto flash memory area EB2 (H'FFF000–
H'FFF3FF).
H'000000
Block area
H'000800
EB2
area
H'000BFF
H'000FFF
Note: * When part of RAM (H'FFF000–H'FFF3FF) is overlapped onto a flash memory small block area, the flash
memory in the overlapped area cannot be accessed. It can be accessed when the overlapping is
cleared.
614
Flash memory
space
Overlapping ram
(Mapping RAM
*
H'FFEF20
On-chip RAM
H'FFEFFF
H'FFF000
(Actual RAM
H'FFF3FF
H'FFF400
H'FFFF1F

Figure 19.14 Example of RAM Overlap Operation

Procedure:
1. Part of RAM
(H'FFF000–H'FFF3FF) is
overlapped onto the area (EB2)
requiring real-time programming
(RAMCR bits 3 to 1 are set to 1, 1,
0, and the flash memory area to be
overlapped (EB2) is selected).
2. Real-time programming is
performed using the overlapping
area)
RAM.
3. The programmed data is checked,
then RAM overlapping is cleared
(RAMS bit is cleared).
4. The data written in RAM area
H'FFF000–H'FFF3FF is written to
flash memory space.
area
area)