M29W320ET, M29W320EB
STATUS REGISTER
The M29W320E has one Status Register. It pro-
vides information on the current or previous Pro-
gram or Erase operations. The various bits convey
information and errors on the operation. Bus Read
operations from any address, always read the Sta-
tus Register during Program and Erase opera-
tions. It is also read during Erase Suspend when
an address within a block being erased is access-
ed.
Error Bit (DQ5). The Error Bit can be used to
identify errors detected by the Program/Erase
Controller. The Error Bit is set to ’1’ when a Pro-
gram, Block Erase or Chip Erase operation fails to
write the correct data to the memory. If the Error
Bit is set a Read/Reset command must be issued
before other commands are issued. The Error bit
is output on DQ5 when the Status Register is read.
Note that the Program command cannot change a
bit set to ’0’ back to ’1’ and attempting to do so will
set DQ5 to ‘1’. A Bus Read operation to that ad-
dress will show the bit is still ‘0’. One of the Erase
commands must be used to set all the bits in a
block or in the whole memory from ’0’ to ’1’.
Erase Timer Bit (DQ3). The Erase Timer Bit can
be used to identify the start of Program/Erase
Controller operation during a Block Erase com-
mand. Once the Program/Erase Controller starts
erasing the Erase Timer Bit is set to ’1’. Before the
Program/Erase Controller starts the Erase Timer
Bit is set to ’0’ and additional blocks to be erased
may be written to the Command Interface. The
Erase Timer Bit is output on DQ3 when the Status
Register is read.
The bits in the Status Register are summarized in
Table 7., Status Register Bits.
Data Polling Bit (DQ7). The Data Polling Bit can
be used to identify whether the Program/Erase
Controller has successfully completed its opera-
tion or if it has responded to an Erase Suspend.
The Data Polling Bit is output on DQ7 when the
Status Register is read.
During Program operations the Data Polling Bit
outputs the complement of the bit being pro-
grammed to DQ7. After successful completion of
the Program operation the memory returns to
Read mode and Bus Read operations from the ad-
dress just programmed output DQ7, not its com-
plement.
Alternative Toggle Bit (DQ2). The Alternative
Toggle Bit can be used to monitor the Program/
Erase controller during Erase operations. The Al-
ternative Toggle Bit is output on DQ2 when the
Status Register is read.
During Chip Erase and Block Erase operations the
Toggle Bit changes from ’0’ to ’1’ to ’0’, etc., with
successive Bus Read operations from addresses
within the blocks being erased. A protected block
is treated the same as a block not being erased.
Once the operation completes the memory returns
to Read mode.
During Erase Suspend the Alternative Toggle Bit
changes from ’0’ to ’1’ to ’0’, etc. with successive
Bus Read operations from addresses within the
blocks being erased. Bus Read operations to ad-
dresses within blocks not being erased will output
the memory cell data as if in Read mode.
During Erase operations the Data Polling Bit out-
puts ’0’, the complement of the erased state of
DQ7. After successful completion of the Erase op-
eration the memory returns to Read Mode.
In Erase Suspend mode the Data Polling Bit will
output a ’1’ during a Bus Read operation within a
block being erased. The Data Polling Bit will
change from a ’0’ to a ’1’ when the Program/Erase
Controller has suspended the Erase operation.
Figure 7., Data Polling Flowchart, gives an exam-
ple of how to use the Data Polling Bit. A Valid Ad-
dress is the address being programmed or an
address within the block being erased.
Toggle Bit (DQ6). The Toggle Bit can be used to
identify whether the Program/Erase Controller has
successfully completed its operation or if it has re-
sponded to an Erase Suspend. The Toggle Bit is
output on DQ6 when the Status Register is read.
After an Erase operation that causes the Error Bit
to be set the Alternative Toggle Bit can be used to
identify which block or blocks have caused the er-
ror. The Alternative Toggle Bit changes from ’0’ to
’1’ to ’0’, etc. with successive Bus Read Opera-
tions from addresses within blocks that have not
erased correctly. The Alternative Toggle Bit does
not change if the addressed block has erased cor-
rectly.
During Program and Erase operations the Toggle
Bit changes from ’0’ to ’1’ to ’0’, etc., with succes-
sive Bus Read operations at any address. After
successful completion of the operation the memo-
ry returns to Read mode.
During Erase Suspend mode the Toggle Bit will
output when addressing a cell within a block being
erased. The Toggle Bit will stop toggling when the
Program/Erase Controller has suspended the
Erase operation.
Figure 14. and Figure 15. describe Alternative
Toggle Bit timing waveform.
Figure 8., Toggle Flowchart, gives an example of
how to use the Data Toggle Bit. Figure 14. and
Figure 15. describe Toggle Bit timing waveform.
19/46
STMICROELECTRONICS [ ST ]
