TMS29LF040, TMS29VF040

524288 BY 8BIT

FLASH MEMORIES

SMJS825D − SEPTEMBER 1995 − REVISED JUNE 1998

11

POST OFFICE BOX 1443

data protection

hardware-sector protection 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. The sector-unprotect mode is available to unprotect

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

sector-protect operation

the sector to be protected. Address pins A0−A8, A10−A15, and I/O pins DQ0−DQ7 must be stable and can be

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. If the sector selected is not protected, the DQs output 00h.

sector-unprotect operation

Prior to a sector-unprotect operation, all sectors should be protected using the sector-protect mode.

stable, W is pulsed low for 10 ms. The unprotect operation begins on the falling edge of W and terminates on

the rising edge of W. Figure 17 shows a timing diagram of the sector-unprotect operation.

sector-unprotect verify

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

glitching

Pulses of less than 5 ns (typical) on G, W, or E do not issue a write cycle.

power supply considerations

Each device should have a 0.1-