H8-3857 Datasheet, PDF (188/560 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcomputer

6. ROM
6.9 Flash Memory Programming and Erasing Precautions
Precautions concerning the use of on-board programming mode and Writer mode are summarized
below.
1. Use the specified voltages and timing for programming and erasing.
Applying a voltage in excess of the rating can permanently damage the device. Use a PROM
programmer that supports the Renesas Technology microcomputer device type with 64-kbyte
on-chip flash memory.
Do not select the HN28F101 setting for the PROM programmer, and only use the specified
socket adapter. Incorrect use may damage the device.
2. Powering on and off
Do not apply a high level to the FWE pin until V_CC has stabilized. Also, drive the FWE pin low
before turning off V_CC.
When applying or disconnecting V_CC, 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. Failure to do so may result in overprogramming or
overerasing due to MCU runaway, and loss of normal memory cell operation.
3. FWE application/disconnection
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:
a. Apply FWE when the V_CC voltage has stabilized within its rated voltage range.
b. Apply FWE when oscillation has stabilized (after the elapse of the oscillation stabilization
time).
c. In boot mode, apply and disconnect FWE during a reset.
d. 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 program execution in flash memory.
e. Do not apply FWE if program runaway has occurred.
f. Disconnect FWE only when the SWE, ESU, PSU, EV, PV, P, and E bits in FLMCR1 and
FLMCR2 are cleared.
Make sure that the SWE, ESU, PSU, EV, PV, P, and E bits are not set by mistake when
applying or disconnecting FWE.
Rev.3.00 Jul. 19, 2007 page 164 of 532
REJ09B0397-0300