Datasheet

Section 20 Flash Memory (F-ZTAT Version)
Rev. 6.00 Mar. 18, 2010 Page 746 of 982
REJ09B0054-0600
Do not select the HN27C4096 setting for the PROM programmer, and only use the specified
socket adapter. Failure to observe these points may result in damage to the device.
Powering On and Off (See Figures 20.14 to 20.16): Do not apply a high level to the FWE pin
until VCC has stabilized. Also, drive the FWE pin low before turning off VCC.
When applying or disconnecting VCC power, fix the FWE pin low and place the flash memory in
the hardware protection state.
The power-on and power-off timing requirements should also be satisfied in the event of a power
failure and subsequent recovery.
FWE Application/Disconnection (See Figures 20.14 to 20.16): FWE application should be
carried out when MCU operation is in a stable condition. If MCU operation is not stable, fix the
FWE pin low and set the protection state.
The following points must be observed concerning FWE application and disconnection to prevent
unintentional programming or erasing of flash memory:
• Apply FWE when the VCC voltage has stabilized within its rated voltage range.
• In boot mode, apply and disconnect FWE during a reset.
• In user program mode, FWE can be switched between high and low level regardless of the
reset state. FWE input can also be switched during execution of a program in flash memory.
• Do not apply FWE if program runaway has occurred.
• Disconnect FWE only when the SWE1, ESU1, PSU1, EV1, PV1, P1, and E1 bits in FLMCR1
are cleared.
Make sure that the SWE1, ESU1, PSU1, EV1, PV1, P1, and E1 bits are not set by mistake
when applying or disconnecting FWE.
Do Not Apply a Constant High Level to the FWE Pin: Apply a high level to the FWE pin only
when programming or erasing flash memory. 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.
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 P1 or E1 bit in
FLMCR1, the watchdog timer should be set beforehand as a precaution against program runaway,
etc.