Renesas H8S/2318 series, Hardware Manual

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Rev. 5.00, 12/03, page 593 of 1088
state, setting the P or E bit in flash memory control register 1 (FLMCR1) will not cause
a transition to program mode or erase mode. When actually programming 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.
17.10 Interrupt Handling when Programming/Erasing Flash Memory
All interrupts, including NMI input, are disabled when flash memory is being programmed or
erased (when the P or E bit is set in FLMCR1), and while the boot program is executing in boot
mode*
1
, to give priority to the program or erase operation. There are three reasons for this:
1. Interrupt during programming or erasing might cause a violation of the programming or
erasing algorithm, with the result that normal operation could not be assured.
2. In the interrupt exception handling sequence during programming or erasing, the vector would
not be read correctly*
2
, possibly resulting in MCU runaway.
3. If an interrupt occurred during boot program execution, it would not be possible to execute the
normal boot mode sequence.
For these reasons, in on-board programming mode alone there are conditions for disabling
interrupts, as an exception to the general rule. However, this provision does not guarantee normal
erasing and programming or MCU operation. All interrupt requests, including NMI, must
therefore be restricted inside and outside the MCU when programming or erasing flash memory.
The NMI interrupt is also disabled in the error-protection state while the P or E bit remains set in
FLMCR1.
Notes: 1. Interrupt requests must be disabled inside and outside the MCU until the programming
control program has completed programming.
2. The vector may not be read correctly in this case for the following two reasons:
• If flash memory is read while being programmed or erased (while the P or E bit is
set in FLMCR1), correct read data will not be obtained (undetermined values will
be returned).
• If the interrupt entry in the vector table has not been programmed yet, interrupt
exception handling will not be executed correctly.