MBM29DL400BC Fujitsu Media Devices, MBM29DL400BC Datasheet - Page 13

• Manufacturer Part Number: MBM29DL400BC
• Description: 4M (512K X 8/256K X 16) BIT
• Manufacturer: Fujitsu Media Devices

Write
Sector Protection
Temporary Sector Unprotection
Device erasure and programming are accomplished via the command register. The contents of the register serve
as inputs to the internal state machine. The state machine outputs dictate the function of the device.
The command register itself does not occupy any addressable memory location. The register is a latch used to
store the commands, along with the address and data information needed to execute the command. The
command register is written by bringing WE to V
the falling edge of WE or CE, whichever happens later; while data is latched on the rising edge of WE or CE,
whichever happens first. Standard microprocessor write timings are used.
Refer to AC Write Characteristics and the Erase/Programming Waveforms for specific timing parameters.
The MBM29DL400TC/BC feature hardware sector protection. This feature will disable both program and erase
operations in any number of sectors (0 through 13). The sector protection feature is enabled using programming
equipment at the user’s site. The devices are shipped with all sectors unprotected. Alternatively, Fujitsu may
program and protect sectors in the factory prior to shiping the device.
To activate this mode, the programming equipment must force V
V
be set to the sector to be protected. Tables 6 and 7 define the sector address for each of the forteen (14)
individual sectors. Programming of the protection circuitry begins on the falling edge of the WE pulse and is
terminated with the rising edge of the same. Sector addresses must be held constant during the WE pulse. See
Figures 16 and 25 for sector protection waveforms and algorithm.
To verify programming of the protection circuitry, the programming equipment must force V
with CE and OE at V
A
devices will read 00H for unprotected sector. In this mode, the lower order addresses, except for A
are DON’T CARES. Address locations with A
A
It is also possible to determine if a sector is protected in the system by writing an Autoselect command. Performing
a read operation at the address location XX02H, where the higher order addresses (A
A
5.2 for Autoselect codes.
This feature allows temporary unprotection of previously protected sectors of the MBM29DL400TC/BC devices
in order to change data. The Sector Unprotection mode is activated by setting the RESET pin to high voltage
(12 V). During this mode, formerly protected sectors can be programmed or erased by selecting the sector
addresses. Once the 12 V is taken away from the RESET pin, all the previously protected sectors will be protected
again. See Figures 17 and 26.
MBM29DL400TC
ID
1
-1
12
, A
) are the desired sector address will produce a logical “1” at DQ
requires to apply to V
= 11.5 V), CE = V
0
) = (0, 1, 0) will produce a logical “1” code at device output DQ
IL
IL
, and A
and WE at V
IL
on byte mode.
0
= A
6
IH
= V
. Scanning the sector addresses (A
-55/-70/-90/-12
IL
, A
1
= V
1
= V
IH
IL
. The sector addresses (A
, while CE is at V
IL
are reserved for Autoselect manufacturer and device codes.
/MBM29DL400BC
ID
on address pin A
IL
0
and OE is at V
for a protected sector. See Tables 5.1 and
0
17
for a protected sector. Otherwise the
, A
17
16
, A
, A
16
15
, A
9
IH
and control pin OE, (suggest
, A
. Addresses are latched on
15
, A
14
, A
17
14
, A
, A
13
ID
, and A
16
13
, A
on address pin A
-55/-70/-90/-12
, and A
15
, A
12
0
, A
14
) while (A
12
, A
1
) should
, and A
13
, and
6
9
6
,
13