HD6433044 Datasheet, PDF (618/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

The error-protect state can be cleared only by a reset or entry to hardware standby mode.
Note: * It is possible to write to these registers. Note that a transition to software standby mode
initializes these registers.
Memory read
or verify mode
RD VF PR ER
FLER = 0
RES = 0 or STBY = 0
or software standby
RES = 1 and STBY = 1
and not software standby
P = 1 or E = 1 _{P = 0 and E = 0}
RES = 0 or
STBY = 0
Program mode
or erase mode
RES = 0 or
STBY = 0
RD VF PR ER
FLER = 0
Error occurs
(software standby)
Reset or standby
(hardware protect)
RD VF PR ER
INIT.
FLER = 0
RES = 0 or
STBY = 0
Error occurs
RD: Memory read enabled
VF: Verify read enabled
PR: Programming enabled
Error-protect mode
ER: Erase enabled
RD: Memory read disabled
VF: Verify read disabled
RD VF PR ER
FLER = 1
PR: Programming disabled
ER: Erase disabled
INIT.: Initialized state of registers (FLMCR, EBR1, EBR2)
Software
standby
Error-protect mode
(software standby)
RD VF PR ER
INIT.
FLER = 1
Software standby
cleared
Figure 18-19 Flash Memory State Transitions in Modes 5, 6 and 7 (On-Chip ROM
Enabled) when Programming Voltage (V_PP) is Applied
The purpose of error-protect mode is to prevent overprogramming or overerasing damage to flash
memory by detecting abnormal conditions that occur if the programming or erasing algorithm is
not followed, or if a program crashes while the flash memory is being programmed or erased.
This protection function does not cover abnormal conditions other than the setting conditions of
the flash memory error bit (FLER), however. Also, if too much time elapses before the error-
protect state is reached, the flash memory may already have been damaged. This function
accordingly does not offer foolproof protection from damage to flash memory.
To prevent abnormal operations, when programming voltage (V_PP) is applied, follow the
programming and erasing algorithms correctly, and keep microcontroller operations under
constant internal and external supervision, using the watchdog timer for example. If a transition to
error-protect mode occurs, the flash memory may contain incorrect data due to errors in
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