MBM29F400TC-55/-70/-90/MBM29F400BC-55/-70/-90
DQ7
Data Polling
The MBM29F400TC/BC device feature Data Polling as a method to indicate to the host that the Embedded
Algorithms are in progress or completed. During the Embedded Program Algorithm an attempt to read the device
will produce the complement of the data last written to DQ7. Upon completion of the Embedded Program
Algorithm, an attempt to read the device will produce the true data last written to DQ7. During the Embedded
Erase Algorithm, an attempt to read the device will produce a “0” at the DQ7 output. Upon completion of the
Embedded Erase Algorithm an attempt to read the device will produce a “1” at the DQ7 output. The flowchart
for Data Polling (DQ7) is shown in Figure 21.
For Programing, the Data Polling is valid after the rising edge of fourth write pulse in the four write pulse sequence.
For chip erase and sector erase, the Data Polling is valid after the rising edge of the sixth write pulse in the six
write pulse sequence. Data Polling must be performed at sector address within any of the sectors being erased
and not a protected sector. Otherwise, the status may not be valid. Once the Embedded Algorithm operation is
close to being completed, the MBM29F400TC/BC data pins (DQ7) may change asynchronously while the output
enable (OE) is asserted low. This means that the device is driving status information on DQ7 at one instant of
time and then that byte’s valid data at the next instant of time. Depending on when the system samples the DQ7
output, it may read the status or valid data. Even if the device has completed the Embedded Algorithm operation
and DQ7 has a valid data, the data outputs on DQ0 to DQ6 may be still invalid. The valid data on DQ0 to DQ7 will
be read on the successive read attempts.
TheDataPollingfeatureisonlyactiveduringtheEmbeddedProgrammingAlgorithm,EmbeddedEraseAlgorithm
or sector erase time-out (See Table 8).
See Figure 9 for the Data Polling timing specifications and diagrams.
DQ6
Toggle Bit I
The MBM29F400TC/BC also feature the “Toggle Bit I” as a method to indicate to the host system that the
Embedded Algorithms are in progress or completed.
During an Embedded Program or Erase Algorithm cycle, successive attempts to read (OE toggling) data from
the device will result in DQ6 toggling between one and zero. Once the Embedded Program or Erase Algorithm
cycle is completed, DQ6 will stop toggling and valid data will be read on the next successive attempts. During
programming, theToggleBitIisvalidaftertherisingedgeofthefourthwritepulseinthefourwritepulsesequence.
For chip erase and sector erase, the Toggle Bit I is valid after the rising edge of the sixth write pulse in the six
write pulse sequence. The Toggle Bit I is active during the sector time out.
In programming, if the sector being written to is protected, the toggle bit l will toggle for about 2 µs and then stop
toggling without the data having changed. In erase, the device will erase all the selected sectors except for the
ones that are protected. If all selected sectors are protected, the chip will toggle the toggle bit for about 100 µs
and then drop back into read mode, having changed none of the data.
Either CE or OE toggling will cause the DQ6 to toggle. In addition, an Erase Suspend/Resume command will
cause DQ6 to toggle.
See Figure 10 for the Toggle Bit I timing specifications and diagrams.
DQ5
Exceeded Timing Limits
DQ5 will indicate if the program or erase time has exceeded the specified limits (internal pulse count). Under
these conditions DQ5 will produce a “1”. This is a failure condition which indicates that the program or erase
cycle was not successfully completed. Data Polling is the only operating function of the devices under this
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