19.20.2 Ram Overlap - Renesas H8S Series Hardware Manual

16-bit single-chip microcomputer

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19.20.2 RAM Overlap

An example in which flash memory block area EB1 is overlapped is shown below.

Example in Which Flash Memory Block Area EB1 is Overlapped

1. Set bits RAMS, RAM2, RAM1, and RAM0 in RAMER to 1, 0, 0, 1, to overlap part of RAM onto the area (EB1) for

which real-time programming is required.

2. Real-time programming is performed using the overlapping RAM.

3. After the program data has been confirmed, the RAMS bit is cleared, releasing RAM overlap.

4. The data written in the overlapping RAM is written into the flash memory space (EB1).

Notes: 1. When the RAMS bit is set to 1, program/erase protection is enabled for all blocks regardless of the value of

RAM2, RAM1, and RAM0 (emulation protection). In this state, setting the P or E bit in flash memory control

a flash memory area, the RAMS bit should be cleared to 0.

2. A RAM area cannot be erased by execution of software in accordance with the erase algorithm while flash

memory emulation in RAM is being used.

3. Block area EB0 includes the vector table. When performing RAM emulation, the vector table is needed by the

overlap RAM.

Rev.6.00 Oct.28.2004 page 646 of 1016

REJ09B0138-0600H

Flash memory

Figure 19-52 Example of RAM Overlap Operation

This area can be accessed

from both the RAM area

and flash memory area