MBM29F040C-55/-70/-90
DQ6
Toggle Bit I
The MBM29F040C also features 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, the Toggle Bit I is valid after the rising edge of the fourth WE pulse in the four write pulse sequence.
For chip erase and sector erase, the Toggle Bit I is valid after the rising edge of the sixth WE 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 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 the DQ6 to toggle.
See Figure 10 for the Toggle Bit 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 DQ7, DQ6 is the only operating function of the device 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 Table 2.
The DQ5 failure condition may also appear if a user tries to program a non blank location without erasing. In this
case the device locks out and never completes the Embedded Algorithm operation. Hence, the system never
reads a valid data on DQ7 bit and DQ6 never stops toggling. Once the device has exceeded timing limits, the
DQ5 bit will indicate a “1.” Please note that this is not a device failure condition since the device was 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 I 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.
Refer to Table 6: Hardware Sequence Flags.
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