HD64F3437TF16 Datasheet, PDF (422/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

User Programming Mode Execution Procedure (Example)*: Figure 19.7 shows the execution
procedure for user programming mode when the on-board update routine is executed in RAM.
Note: * Do not apply 12 V to the FV_PP pin during normal operation. To prevent flash memory
from being accidentally programmed or erased due to program runaway etc., apply 12 V
to FV_PP only when programming or erasing flash memory. Overprogramming or
overerasing due to program runaway can cause memory cells to malfunction. While 12 V
is applied, the watchdog timer should be running and enabled to halt runaway program
execution, so that program runaway will not lead to overprogramming or overerasing. For
details on applying, releasing, and shutting off V_PP, see section 19.7, Flash Memory
Programming and Erasing Precautions (5).
Set MD₁ and MD₀ to 10 or 11
1
(apply V_IH to V_CC to MD₁)
Start from reset
Branch to flash memory
2
on-board update program
3
Transfer on-board update routine
into RAM
Branch to flash memory on-board
4
update routine in RAM
5
FV_PP = 12 V
(user programming mode)
Execute flash memory
6
on-board update routine in RAM
(update flash memory)
7
Release FV_PP
(exit user programming mode)
8
Branch to application program
in flash memory*
Procedure
The flash memory on-board update
program is written in flash memory ahead
of time by the user.
1. Set MD1 and MD0 of the H8/3434F to
10 or 11, and start from a reset.
2. Branch to the flash memory on-board
update program in flash memory.
3. Transfer the on-board update routine
into RAM.
4. Branch to the on-board update routine
that was transferred into RAM.
5. Apply 12 V to the FV_PP pin, to enter
user programming mode.
6. Execute the flash memory on-board
update routine in RAM, to perform an
on-board update of the flash memory.
7. Change the voltage at the FV_PP pin
from 12 V to V_CC, to exit user
programming mode.
8. After the on-board update of flash
memory ends, execution branches to
an application program in flash
memory.
Note: * After the update is finished, when input of 12 V to the FV_PP pin is released, the flash
memory read setup time (t_FRS) must elapse before any program in flash memory is
executed. This is the required setup time from when the FV_PP pin reaches the (V_CC +
2 V) level after 12 V is released until flash memory can be read.
Figure 19.7 User Programming Mode Operation (Example)
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