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17.9
Flash Memory Programming and Erasing Precautions
Precautions concerning the use of on-board programming mode, the RAM emulation function, and
PROM mode are summarized below.
1. Use the specified voltages and timing for programming and erasing.
Applied voltages in excess of the rating can permanently damage the device. Use a PROM
programmer that supports the Hitachi microcomputer device type with 128-kbyte on-chip flash
memory.
Do not select the HN28F101 setting for the PROM programmer. An incorrect setting will result in
application of a high level to the FWE pin, damaging the device.
2. Powering on and off (see figures 17.16 to 17.18)
Do not apply a high level to the FWE pin until V
before turning off V
CC
When applying or disconnecting V
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 (see figures 17.16 to 17.18)
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 V
If FWE is applied when the MCU's V
MCU operation will be unstable and flash memory may be erroneously programmed or erased.
• Apply FWE when oscillation has stabilized (after the elapse of the oscillation settling time).
power is turned on, hold the RES pin low for the duration of the oscillation settling
When V
CC
time (t
= 20 ms) before applying FWE. Do not apply FWE when oscillation has stopped or
OSC1
is unstable.
• In boot mode, apply and disconnect FWE during a reset.
In a transition to boot mode, FWE = 1 input and MD
while the RES input is low. FWE and MD
programming setup time (t
.
power, fix the FWE pin low and place the flash memory in
CC
voltage has stabilized within its rated voltage range.
CC
CC
) with respect to the reset release timing. When making a
MDS
has stabilized. Also, drive the FWE pin low
CC
power supply is not within its rated voltage range,
to MD
2
0
to MD
pin input must satisfy the mode
2
0
setting should be performed
515
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