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In user program mode, FWE can be switched between high and low level regardless of
RES input.
FWE input can also be switched during execution of a program in flash memory.
•
Do not apply FWE if program runaway has occurred.
During FWE application, the program execution state must be monitored using the
watchdog timer or some other means.
•
Disconnect FWE only when the SWE, ESU, PSU, EV, PV, E, and P bits in FLMCR1 are
cleared.
Make sure that the SWE, ESU, PSU, EV, PV, E, and P bits are not set by mistake when
applying or disconnecting FWE.
4. Do not apply a constant high level to the FWE pin.
T prevent erroneous programming or erasing due to program runaway, etc., apply a high level
to the FWE pin only when programming or erasing flash memory (including execution of flash
memory emulation using RAM). A system configuration in which a high level is constantly
applied to the FWE pin should be avoided. Also, while a high level is applied to the FWE pin,
the watchdog timer should be activated to prevent overprogramming or overerasing due to
program runaway, etc.
5. Use the recommended algorithm when programming and erasing flash memory.
The recommended algorithm enables programming and erasing to be carried out without
subjecting the device to voltage stress or sacrificing program data reliability. When setting the
PSU or ESU bit in FLMCR1, the watchdog timer should be set beforehand as a precaution
against program runaway, etc.
Also note that access to the flash memory space by means of a MOV instruction, etc., is not
permitted while the P bit or E bit is set.
6. Do not set or clear the SWE bit during execution of a program in flash memory.
Clear the SWE bit before executing a program or reading data in flash memory. When the
SWE bit is set, data in flash memory can be rewritten, but flash memory should only be
accessed for verify operations (verification during programming/erasing).
Similarly, when using the RAM emulation function while a high level is being input to the
FWE pin, the SWE bit must be cleared before executing a program or reading data in flash
memory. However, the RAM area overlapping flash memory space can be read and written to
regardless of whether the SWE bit is set or cleared.
A wait time is necessary after the SWE bit is cleared. For details see table 22.40 in section
22.5.6, Flash Memory Characteristics.
7. Do not use interrupts while flash memory is being programmed or erased.
All interrupt requests, including NMI, should be disabled during FWE application to give
priority to program/erase operations (including emulation in RAM).
Bus release must also be disabled.
619
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