ISSUE 4.7 : NOVEMBER 1998
MFM8516 - 70/90/12/15
Sector Protection
The MFM8516 features hardware sector protection. This feature will disable both program and erase opera-
tions in any number of sectors (0 through 8). The sector protect feature is enabled using programming equip-
ment at the users site. The device is shipped with all sectors unprotected.
It is also possible to determine if a sector is protected in the system by writing the Autoselect command.
Performing a read operation at the address location XX02H, where the higher order addresses (A16, A17,
A18) are the sector addresses will produce a logical "1" at D0 for a protected sector.
Sector Address Table
A18
A17
A16
Address Range
SA0
SA1
SA2
SA3
SA4
SA5
SA6
SA7
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
00000h-0FFFFh
10000h-1FFFFh
20000h-2FFFFh
30000h-3FFFFh
40000h-4FFFFh
50000h-5FFFFh
60000h-6FFFFh
70000h-7FFFFh
Sector Unprotect
The MFM8516 also features a sector unprotect mode so that a potected sector may be unprotected to
incorporate any changes in the code. The sector unprotect is enabled using programming equipment at the
user's site. It is also possible to determine if a sector is unprotected in the system by writing the autoselect
command and A6 is set at VIH. Performing a read operation at address location XXX2H, where the higher
order addresses (A18, A17, and A16) define a particular sector address, will produce 00H at data outputs (D0
- D7) for an unprotected sector.
Autoselect Command
Flash memories are intended for use in applications where the local CPU alters memory contents. PROM
programmers typically access the signature codes by raising A9 to a high voltage. However, multiplexing high
voltage onto the address lines is not generally a desired system design practice.
The device contains an autoselect operation to supplement traditional PROM programming methodology. The
operation is initiated by writing the autoselect command sequence into the command register.
Following command write, scanning the sector addresses on A16, A17, & A18 while A6, A1 & A0 = 0, 1, 0 will
produce a logical "1" at device output D0 for a protected sector.
To terminate the operation, it is necessary to write the read/reset command sequence into the register.
16
MOSAIC [ MOSAIC ]
