TMS29F002B Datasheet, PDF (12/38 Pages) Texas Instruments – 262144 BY 8-BIT FLASH MEMORIES

TMS29F002T, TMS29F002B
262144 BY 8-BIT
FLASH MEMORIES
SMJS848 – AUGUST 1997
exceed time limit (DQ5)
The program and erase operations use an internal-pulse counter to limit the number of pulses applied. If the
pulse-count limit is exceeded, DQ5 is set to a logic-high data state, indicating that the program or erase
operation has failed. DQ7 does not change from complemented data to true data and DQ6 does not stop
toggling when read. To continue operation, the device must be reset.
This condition occurs when attempting to program a logic-high state into a bit that has been programmed
previously to a logic low. Only an erase operation can change bits from logic low to logic high. After reset, the
device is functional and can be erased and reprogrammed.
sector-load-timer (DQ3)
The sector-load-timer status bit, DQ3, is used to determine whether the time to load additional sector addresses
has expired. After completion of a sector erase command sequence, DQ3 remains at a logic low for 100 µs. This
indicates that another sector-erase command sequence can be issued. If DQ3 is at a logic high, it indicates that
the delay has expired and attempts to issue additional sector-erase commands are ignored. See the
sector-erase command section for a description.
The data-polling and toggle bit are valid during the 100-µs time delay and can be used to determine if a valid
sector-erase command has been issued. To ensure additional sector-erase commands have been accepted,
the status of DQ3 should be read before and after each additional sector-erase command. If DQ3 is at a logic
low on both reads, the additional sector-erase command was accepted.
toggle bit 2 (DQ2)
The state of DQ2 determines whether the device is in algorithmic erase mode or erase-suspend mode. DQ2
toggles if successive reads are issued to the erasing or erase-suspended sector, assuming in case of the latter
that the device is in erase suspend read mode. It also toggles when DQ5 becomes a logic high due to
timer-exceed limit and reads are issued to the failed sector. DQ2 does not toggle in any other sector due to DQ5
fail. When the device is in erase-suspend program mode, successive reads from the non-erase-suspended
sector causes a logic high on DQ2.
sector-protect programming
The sector-protect programming mode is activated when A6, A0, and CE at V_IL, and address pin A9 and control
pin OE are forced to V_ID. Address pin A1 is set to V_IH.The sector-select-address pins A17 – A13 are used to
select the sector to be protected. Address pins A12–A0 and I/O pins must be stable and can be either low or
high. Once the addresses are stable, WE is pulsed low for 100 µs causing programming to begin on the falling
edge of WE and terminate on the rising edge of WE. Figure 16 is a flow chart of the sector-protect algorithm.
Commands to program or erase a protected sector do not change the data contained in the sector. Attempts
to program and erase a protected sector causes data-polling and toggle-bit (DQ6) to operate from 2-µs to
100-µs and then return to valid data.
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