Fujitsu MB91260B Series Hardware Manual page 442

■ Enable Sector Protect
Enable sector protect operation writes into the protection circuit in the flash memory.
By this operation, write and erase operations are invalidated for any combination of ten sectors. For
MB91F264B, the protection is cancelled in all sectors at the factory setting. First in this operation, set
sector addresses (A17, A16, A15, A14, A13) of the sector to be protected to the address signal. For the
sector and sector address, see Table 17.1-1.
Writing to the protection circuit starts by trailing edge of WEX pulse after applying V
and MD0 to set CEX=0, and ends by leading edge.
Keep sector addresses constant during WEX pulse. Once the sector protection is set, it cannot be canceled.
Also, write/erase operations are disables on the protected sector afterward.
■ Verify Sector Protect
Verify sector protect operation verifies the writing to the protection circuit in the flash memory. First, this
operation sets CEX and OEX to "0" and applies V
setting a sector address to the address signal and reading under (A7, A2, A1) = (0, 1, 0) condition, it outputs
"1" to output DQ0 in the protected sector. The value "00
17.6-1 shows the sector protect algorithms using enable sector protect and verify sector protect.
CHAPTER 17 FLASH MEMORY
(margin mode) to MD0 while WEX is "1". When
ID
" is read from the unprotected sector. Table
H
(=12 V) to MD2
ID
427