M29W800AT STMICROELECTRONICS [STMicroelectronics], M29W800AT Datasheet - Page 15

• Manufacturer Part Number: M29W800AT
• Description: 8 Mbit (1Mb x8 or 512Kb x16, Boot Block) Low Voltage Single Supply Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

STATUS REGISTER
P/E.C. status is indicated during execution by Data
Polling on DQ7, detection of Toggle on DQ6 and
DQ2, or Error on DQ5 and Erase Timer DQ3 bits.
Any read attempt during Program or Erase com-
mand execution will automatically output these
five Status Register bits. The P/E.C. automatically
sets bits DQ2, DQ3, DQ5, DQ6 and DQ7. Other
bits (DQ0, DQ1 and DQ4) are reserved for future
use and should be masked. See
Register Bits
Bits.
Data Polling Bit (DQ7). When Programming op-
erations are in progress, this bit outputs the com-
plement of the bit being programmed on DQ7.
During Erase operation, it outputs a '0'. After com-
pletion of the operation, DQ7 will output the bit last
programmed or a '1' after erasing. Data Polling is
valid and only effective during P/E.C. operation,
that is after the fourth W pulse for programming or
after the sixth W pulse for erase. It must be per-
formed at the address being programmed or at an
address within the block being erased. If all the
blocks selected for erasure are protected, DQ7 will
be set to '0' for about 100µs, and then return to the
previous addressed memory data value. See
ure 15., Data Polling Flowchart
13., Data Polling DQ7 AC
also flag the Erase Suspend mode by switching
from '0' to '1' at the start of the Erase Suspend. In
order to monitor DQ7 in the Erase Suspend mode
an address within a block being erased must be
provided. For a Read Operation in Erase Suspend
mode, DQ7 will output '1' if the read is attempted
on a block being erased and the data value on oth-
er blocks. During Program operation in Erase Sus-
pend Mode, DQ7 will have the same behavior as
in the normal program execution outside of the
suspend mode.
Toggle Bit (DQ6). When Programming or Eras-
ing operations are in progress, successive at-
tempts to read DQ6 will output complementary
data. DQ6 will toggle following toggling of either G,
or E when G is low. The operation is completed
when two successive reads yield the same output
data. The next read will output the bit last pro-
grammed or a '1' after erasing. The toggle bit DQ6
is valid only during P/E.C. operations, that is after
the fourth W pulse for programming or after the
sixth W pulse for Erase. If the blocks selected for
erasure are protected, DQ6 will toggle for about
100µs and then return back to Read. DQ6 will be
set to '1' if a Read operation is attempted on an
Erase Suspend block. When erase is suspended
DQ6 will toggle during programming operations in
and
Table 9., Polling and Toggle
Waveforms. DQ7 will
Table 10., Status
and
Figure
Fig-
a block different to the block in Erase Suspend. Ei-
ther E or G toggling will cause DQ6 to toggle. See
Figure 16., Data Toggle Flowchart
14., Data Toggle DQ6, DQ2 AC
Error Bit (DQ5). This bit is set to '1' by the P/E.C.
when there is a failure of programming, block
erase, or chip erase that results in invalid data in
the memory block. In case of an error in block
erase or program, the block in which the error oc-
curred or to which the programmed data belongs,
must be discarded. The DQ5 failure condition will
also appear if a user tries to program a '1' to a lo-
cation that is previously programmed to '0'. Other
Blocks may still be used. The error bit resets after
a Read/Reset (RD) instruction. In case of success
of Program or Erase, the error bit will be set to '0'.
Erase Timer Bit (DQ3). This bit is set to '0' by the
P/E.C. when the last block Erase command has
been entered to the Command Interface and it is
awaiting the Erase start. When the erase timeout
period is finished, after 50µs to 90µs, DQ3 returns
to '1'.
Toggle Bit (DQ2). This toggle bit, together with
DQ6, can be used to determine the device status
during the Erase operations. It can also be used to
identify the block being erased. During Erase or
Erase Suspend a read from a block being erased
will cause DQ2 to toggle. A read from a block not
being erased will set DQ2 to '1' during erase and
to DQ2 during Erase Suspend. During Chip Erase
a read operation will cause DQ2 to toggle as all
blocks are being erased. DQ2 will be set to '1' dur-
ing program operation and when erase is com-
plete. After erase completion and if the error bit
DQ5 is set to '1', DQ2 will toggle if the faulty block
is addressed.
Table 9. Polling and Toggle Bits
Program
Erase
Erase Suspend Read
(in Erase Suspend
block)
Erase Suspend Read
(outside Erase Suspend
block)
Erase Suspend Program
Mode
M29W800AT, M29W800AB
DQ7
DQ7
DQ7
DQ7
0
1
Waveforms.
Toggle
Toggle
Toggle
DQ6
DQ6
1
and
Note 1
Toggle
DQ2
DQ2
N/A
Figure
1
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