TMS29F010

131072 BY 8-BIT

FLASH MEMORY

SMJS840A – NOVEMBER 1997 – REVISED JUNE 1998

10

POST OFFICE BOX 1443

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 1, indicating that the program or erase operation has failed.

DQ7 will not change from complemented data to true data and DQ6 will not stop toggling when read. To continue

operation, the device must be reset.

The exceed-time-limit condition occurs when attempting to program a logic 1 into a bit that has been

programmed previously to a logic 0. Only an erase operation can change bits from logic 0 to logic 1. 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 if the time to load additional sector addresses has

expired. After completion of a sector-erase command sequence, DQ3 remains at a logic 0 for 80

µs. This

indicates that another sector-erase command sequence can be issued. DQ3 set at a logic 1 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 bit and toggle bit are valid during the 80-

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, then the additional sector-erase command was accepted.

data protection

hardware-sector protect feature

This feature disables both programming and erase operations on any combination of one to eight sectors.

Commands to program or erase a protected sector do not change the data contained in the sector. The

data-polling and toggle bits operate for 2

µs to 100 µs and then return to valid data. This feature is enabled using

a flow chart of the sector-protect operation.

The device is delivered with all sectors unprotected; however, sector-unprotect mode is available to unprotect

protected sectors. Figure 16 is a flow chart of the sector-unprotect operation.

sector-protect operation

to select the sector to be protected. Address pins A0–A8, A10–A13, and I/O pins DQ0 – DQ7 must be stable and

edge of W and terminates on the rising edge of W. Figure 15 shows a timing diagram of the sector-protect

operation.

sector-protect verify

selected is protected, the DQs output 01h, and if the sector selected is not protected, the DQs output 00h.