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AM29F002B-90ECB Datasheet(PDF) 10 Page - Advanced Micro Devices |
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AM29F002B-90ECB Datasheet(HTML) 10 Page - Advanced Micro Devices |
10 / 37 page 10 Am29F002/Am29F002N PREL I M I N AR Y Contact an AMD representative to obtain a copy of the appropriate document. The device is shipped with all sectors unprotected. AMD offers the option of programming and protecting sectors at its factory prior to shipping the device through AMD’s ExpressFlash™ Service. Contact an AMD representative for details. It is possible to determine whether a sector is protected or unprotected. See “Autoselect Mode” for details. Temporary Sector Unprotect Note: This feature requites the RESET# pin and is therefore not available on the Am29F002N. This feature allows temporary unprotection of previ- ously protected sectors to change data in-system. The Sector Unprotect mode is activated by setting the RESET# pin to VID. During this mode, formerly pro- tected sectors can be programmed or erased by se- lecting the sector addresses. Once VID is removed from the RESET# pin, all the previously protected sectors are protected again. Figure 1 shows the algo- rithm, and the Temporary Sector Unprotect diagram shows the timing waveforms, for this feature. Figure 1. Temporary Sector Unprotect Operation Hardware Data Protection The command sequence requirement of unlock cycles for programming or erasing provides data protection against inadvertent writes (refer to the Command Defi- nitions table). In addition, the following hardware data protection measures prevent accidental erasure or pro- gramming, which might otherwise be caused by spuri- ous system level signals during VCC power-up and power-down transitions, or from system noise. Low VCC Write Inhibit When VCC is less than VLKO, the device does not ac- cept any write cycles. This protects data during VCC power-up and power-down. The command register and all internal program/erase circuits are disabled, and the device resets. Subsequent writes are ignored until VCC is greater than VLKO. The system must provide the proper signals to the control pins to prevent uninten- tional writes when VCC is greater than VLKO. Write Pulse “Glitch” Protection Noise pulses of less than 5 ns (typical) on OE#, CE# or WE# do not initiate a write cycle. Logical Inhibit Write cycles are inhibited by holding any one of OE# = VIL, CE# = VIH or WE# = VIH. To initiate a write cycle, CE# and WE# must be a logical zero while OE# is a logical one. Power-Up Write Inhibit If WE# = CE# = VIL and OE# = VIH during power up, the device does not accept commands on the rising edge of WE#. The internal state machine is automatically reset to reading array data on power-up. START Perform Erase or Program Operations RESET# = VIH Temporary Sector Unprotect Completed (Note 2) RESET# = VID (Note 1) Notes: 1. All protected sectors unprotected. 2. All previously protected sectors are protected once again. 20818C-4 |
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