HD6433044 Datasheet, PDF (616/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

18.7.7 Prewrite-Verify Mode
Prewrite-verify mode is a verify mode used after writing 0 to all bits to equalize their threshold
voltages before erasure.
To program all bits, write H'00 in accordance with the algorithm shown in figure 18-17. Use this
procedure to set all data in the flash memory to H'00 after programming. After the necessary
programming time has elapsed, exit program mode (by clearing the P bit to 0) and select prewrite-
verify mode (leave the P, E, PV, and EV bits all cleared to 0). In prewrite-verify mode, a prewrite-
verify voltage is applied to the memory cells at the read address. If the flash memory is read in
this state, the data at the read address will be read. After selecting prewrite-verify mode, wait 4 µs
before reading.
Note: For a sample prewriting program, see the sample erasing program.
18.7.8 Protect Modes
Flash memory can be protected from programming and erasing by software or hardware methods.
These two protection modes are described below.
Software Protection: Prevents transitions to program mode and erase mode even if the P or E bit
is set in the flash memory control register (FLMCR). Details are as follows.
Function
Protection Description
Program Erase
Verify*¹
Block
protect
Individual blocks can be erase and
program-protected by the erase block
registers (EBR1 and EBR2). If EBR1 and
EBR2 are both set to H'00, all blocks are
erase- and program-protected.
Disabled Disabled Enabled
Emulation
protect
When the RAMS bit is set in the RAM
control register (RAMCR), all blocks are
protected from both programming and
erasing.
Disabled*² Disabled*³ Enabled*²
Notes: 1. Three modes: program-verify, erase-verify, and prewrite-verify.
2. Except in RAM areas overlapped onto flash memory.
3. All blocks are erase-disabled. It is not possible to specify individual blocks.
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