Renesas Hitachi H8S/2191, Hardware Manual

Page: 194 / 1065

Rev. 2.0, 11/00, page 167 of 1037
7.9 Flash Memory Programming and Erasing Precautions
Precautions concerning the use of on-board programming mode and programmer 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 Hitachi microcomputer device type with 128-kbyte on-chip flash
memory.
Do not select the HN28F101 setting for the PROM programmer, and only use the specified
socket adapter. Incorrect use will result in damaging 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.
(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) In boot mode, apply and disconnect FWE during a reset.
(c) 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.
(d) Do not apply FWE if program runaway has occurred.
(e) 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.
(4) 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 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.