Table of Contents
Advertisement
19.11
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.
2. Powering on and off (see figures 19.16 to 19.18)
Do not apply a high level to the FWE pin until V
before turning off V
When applying or disconnecting V
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:
•
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
When V
CC
settling time before applying FWE. Do not apply FWE when oscillation has stopped or 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
transition from boot mode to another mode, also, a mode programming setup time is
necessary with respect to the reset release timing.
In a reset during operation, the RES pin must be held low for a minimum of 20 system
clock cycles.
612
.
CC
power, fix the FWE pin low and place the flash memory
CC
voltage has stabilized within its rated voltage range.
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,
CC
–MD
2
–MD
pin input must satisfy the mode
2
0
setting should be performed
0
Advertisement
Table of Contents
