MBM29LV400TC-70/-90/-12/MBM29LV400BC-70/-90/-12
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
condition. The CE circuit will partially power down the device under these conditions (to approximately 2 mA).
The OE and WE pins will control the output disable functions as described in Tables 2 and 3.
The DQ5 failure condition may also appear if a user tries to program a non blank location without erasing. In this
case the devices lock out and never complete the Embedded Algorithm operation. Hence, the system never
reads a valid data on DQ7 bit and DQ6 never stops toggling. Once the devices have exceeded timing limits, the
DQ5 bit will indicate a “1.” Please note that this is not a device failure condition since the devices were incorrectly
used. If this occurs, reset the device with command sequence.
DQ3
Sector Erase Timer
After the completion of the initial sector erase command sequence the sector erase time-out will begin. DQ3 will
remain low until the time-out is complete. Data Polling and Toggle Bit are valid after the initial sector erase
command sequence.
If Data Polling or the Toggle Bit I indicates the device has been written with a valid erase command, DQ3 may
be used to determine if the sector erase timer window is still open. If DQ3 is high (“1”) the internally controlled
erase cycle has begun; attempts to write subsequent commands to the device will be ignored until the erase
operation is completed as indicated by Data Polling or Toggle Bit I. If DQ3 is low (“0”), the device will accept
additional sector erase commands. To insure the command has been accepted, the system software should
check the status of DQ3 prior to and following each subsequent Sector Erase command. If DQ3 were high on
the second status check, the command may not have been accepted.
See Table 9: Hardware Sequence Flags.
DQ2
Toggle Bit II
This toggle bit II, along with DQ6, can be used to determine whether the devices are in the Embedded Erase
Algorithm or in Erase Suspend.
Successive reads from the erasing sector will cause DQ2 to toggle during the Embedded Erase Algorithm. If the
devices are in the erase-suspended-read mode, successive reads from the erase-suspended sector will cause
DQ2 to toggle. When the devices are in the erase-suspended-program mode, successive reads from the byte
address of the non-erase suspended sector will indicate a logic “1” at the DQ2 bit.
DQ6 is different from DQ2 in that DQ6 toggles only when the standard program or Erase, or Erase Suspend
Program operation is in progress. The behavior of these two status bits, along with that of DQ7, is summarized
as follows:
For example, DQ2 and DQ6 can be used together to determine if the erase-suspend-read mode is in progress.
(DQ2 toggles while DQ6 does not.) See also Table 9 and Figure 18.
Furthermore, DQ2 can also be used to determine which sector is being erased. When the device is in the erase
mode, DQ2 toggles if this bit is read from an erasing sector.
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