H8SXSLASH1663R datasheet(1205/1504 Pages) RENESAS

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Section 25 Flash Memory

Rev. 2.00 Sep. 24, 2008 Page 1173 of 1468

REJ09B0412-0200

25.11

Switching between User MAT and User Boot MAT

It is possible to switch between the user MAT and user boot MAT. However, the following

procedure is required because the start addresses of these MATs are allocated to the same address.

Switching to the user boot MAT disables programming and erasing. Programming of the user boot

MAT should take place in boot mode or programmer mode.

1. Memory MAT switching by FMATS should always be executed from the on-chip RAM.

2. When accessing the memory MAT immediately after switching the memory MATs by

FMATS from the on-chip RAM, similarly execute the NOP instruction in the on-chip RAM

for eight times (this prevents access to the flash memory during memory MAT switching).

3. If an interrupt request has occurred during memory MAT switching, there is no guarantee of

which memory MAT is accessed. Always mask the maskable interrupts before switching

memory MATs. In addition, configure the system so that NMI interrupts do not occur during

memory MAT switching.

4. After the memory MATs have been switched, take care because the interrupt vector table will

also have been switched. If interrupt processing is to be the same before and after memory

MAT switching, transfer the interrupt processing routines to the on-chip RAM and specify

VBR to place the interrupt vector table in the on-chip RAM.

5. The size of the user MAT is different from that of the user boot MAT. Addresses which exceed

the size of the 16-Kbyte user boot MAT should not be accessed. If an attempt is made, data is

read as an undefined value.

<On-chip RAM>

Procedure for switching to the user boot MAT

Inhibit interrupts (mask).

Write H'AA to FMATS.

Before access to the user boot MAT, execute the NOP instruction for eight times.

Procedure for switching to the user MAT

Inhibit interrupts (mask).

Write other than H'AA to FMATS.

Before access to the user MAT, execute the NOP instruction for eight times.

Procedure for

switching to

user boot MAT

Procedure for

switching to

user MAT

Figure 25.22 Switching between User MAT and User Boot MAT

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