TMS29F040 datasheet(11/37 Pages) TI

11 / 37 page

TMS29F040

524288 BY 8-BIT

FLASH MEMORY

SMJS820C – APRIL 1996 – REVISED JUNE 1998

POST OFFICE BOX 1443

• HOUSTON, TEXAS 77251–1443

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

high-voltage VID (10.5 V to 12.5 V) on address pin A9 and control pin G, and VIL on control pin E. Figure 14

shows a flow chart of the sector-protect operation.

The device is delivered with all sectors unprotected. Sector-unprotect mode is available to unprotect protected

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

sector-protect operation

The sector-protect operation is activated when VCC = 5.0 V (operating at TA = 25° C), W = VIH, E = VIL, and

address pin A9 and control pin G are forced to VID. The sector-select address pins A16, A17, and A18 are used

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

and can be VIL or VIH. Once the addresses are stable, W is pulsed low for 100 µs. The operation begins on the

falling 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

Verification of sector-protection is activated when VCC = 5.0 V (operating at TA = 25° C), W = VIH, G = VIL,

E = VIL, and address pin A9 = VID. Address pins A0 and A6 are set to VIL, and A1 is set to VIH. Sector-address

pins A16, A17, and A18 select the sector to be verified. The other address pins can be VIH or VIL. If the sector

selected is protected, the DQs output 01h and 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.

Sector-unprotect is activated when VCC = 5.0 V (operating at TA = 25° C), W = VIH, and address pin A9 and

control pins G and E are forced to VID. Address pins A6, A12, and A16 are set to VIH. The sector-select address

pins A17 and A18 can be VIL or VIH. All eight sectors are unprotected in parallel. Once the inputs are 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

Verification of the sector-unprotection is activated when VCC = 5.0 V (operating at TA = 25° C), W = VIH,

G = VIL, E = VIL, and address pin A9 = VID. Select the sector to be verified. Address pins A1 and A6 are set to

VIH, and A0 is set to VIL. The other address pins can be VIH or VIL. If the sector that is selected is protected,

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

low VCC write lockout

During power up and power down, write operations are locked out for VCC less than VLKO. If VCC < VLKO, the

command input is disabled and the device is reset to the read mode. On power up, if E = VIL, W = VIL, and

G = VIH, the device does not accept commands on the rising edge of W. The device automatically powers up

in the read mode.

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-

µF ceramic capacitor connected between VCC and VSS to suppress circuit noise.

Printed-circuit traces to VCC should be appropriate to handle the current demand and minimize inductance.

TMS29F040 Datasheet(PDF) 11 Page - Texas Instruments

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