M39432 Datasheet, PDF (13/28 Pages) STMicroelectronics – Single Chip 4 Mbit Flash Memory and 256 Kbit Parallel EEPROM

M39432
Table 9. Flash Sector Protection
EF EE G W A0 A1 A6 A9 A12 A16 A17 A18
DQ0 - DQ7
V_IL V_IH V_ID V_IL
X
X
X VID X SA SA SA
Protection Activation
Verify Sector Protection Status:
V_IL V_IH V_IL V_IH V_IL V_IH V_IL V_ID X SA SA SA
when DQ0=1, the sector is
protected
Note: 1. X = Don’t Care
2. SA = Sector address
be addressed to a whole sector. Either one sector
(or more) can be explicitly selected for erasure, or
the Bulk Erase instruction can be used to erase all
the sectors in the Flash memory block.
During an Erase cycle, the memory status may be
checked by reading the status bits DQ7, DQ6 and
DQ5, as described on page 8. The Error bit (DQ5)
returns a ’1’ if there has been an Erase Failure (if
the maximum number of Erase cycles has been
exceeded).
The Program instruction to a byte in the Flash
memory block is ignored if it is in a protected
sector. Similarly, the Bulk Erase instruction is
ignored if all the Flash memory sectors are
protected.
If all the addressed sectors, for an Erase
instruction, are protected, nothing is erased. DQ7
and DQ6 are set to ’0’ for about 100 µs, and then
are returned to their values from the previously
addressed byte.
Bulk Erase Instruction. The Bulk Erase
instruction uses six Write operations followed by a
number of Read operations, to read the status
register bits. This is summarized in Table 4. If any
part of the Bulk Erase instruction sequence is
wrong, the device reverts to being in its Read
mode for the Flash memory, and does not execute
the erase instruction.
The M39432 rejects any further instructions that
arrive during the execution of the Bulk Erase
instruction.
Sector Erase Instruction. The Sector Erase
instruction uses six Write operations to specify the
first sector that is to be erased, and an additional
Write operation for each additional sector that is to
be erased in parallel with the first. This is
summarized in Table 4. These Write operations
are transmitted under normal Page Write timing
conditions.
The status of the internal timer can be monitored
on DQ3 (Erase Time-Out bit) as described on
page 10. If DQ3 is ’0’ the Sector Erase instruction
has been received and the timer is counting. If
DQ3 is ’1’, the time-out has expired, and the
M39432 is either in the process of erasing, or has
finished (as indicated on DQ7 and DQ6).
Any instruction arriving before the expiration of the
Erase Time-Out period, other than Erase Suspend
or Erase Resume instruction, aborts the Erase
instruction, and resets the device in its read Flash
memory mode.
During the execution of the Erase instruction, the
Flash memory block accepts only Reset and
Erase Suspend instructions.
Erase Suspend Instruction. When a Sector
Erase cycle is in progress, the Erase Suspend
instruction can be used to suspend the cycle. This
allows the reading of data from another Flash
sector while the Sector Erase instruction is on
hold.
This instruction involves writing B0h at any
address (as shown in Table 4). Erase Suspend is
accepted only during the Sector Erase instruction
execution, and defaults to the Read Flash memory
mode, otherwise. An Erase Suspend instruction
executed during an Erase Time-Out will, in
addition to suspending the Erase, terminate the
time-out period.
Table 10. Flash Unprotection (all sectors)
EF EE G W A0 A1 A6 A9 A12 A16 A17 A18
DQ0 - DQ7
V_ID V_IH V_ID V_IL
X
X
X VID VIH VIH X
X Activation of Unprotected mode
Verify Sector Protection Status:
V_IL V_IH V_IL V_IH V_IL V_IH V_IH V_ID X SA SA SA
when 00h, the sector is
unprotected
Note: 1. X = Don’t Care
2. SA = Sector address
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