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IS23SC4428-X3 Datasheet(PDF) 9 Page - Integrated Silicon Solution, Inc |
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IS23SC4428-X3 Datasheet(HTML) 9 Page - Integrated Silicon Solution, Inc |
9 / 12 page Integrated Silicon Solution, Inc. — 1-800-379-4774 9 REV. A 11/01/01 ISSI® IS23SC4418 IS23SC4428 ISSI® IS23SC4428 SECURITY FEATURES Overview Without entering Programmable Security Code (PSC), only memory read access is possible. However, the content of the PSC addresses (1022 and 1023) cannot be read out. If reading PSC is attempted, 00H will be output. The PSC verification procedure must be performed in the following sequence: 1. Write one to not-written Error Counter bit, address 1021 2. Enter first PSC byte, address 1022 3. Enter second PSC byte, address 1023 4. After successful PSC verification, the Error Counter should be erased to reactivate the 8 PSC entry attempts. If the PSC entry is incorrect, go back to step 1. If all the Error Counter bits have been written, any further PSC entry will be blocked and the memory can never be changed again. Writing Error Counter The number of erased bits (logic 1) in Error Counter determines the number of possible attempts (maximum of eight). Before PSC entry, only writing of error counter is possible. After PSC is successfully verified, the counter can now be erased. Before disconnecting the supply voltage Vcc, the counter should be erased in order to reactivate the eight attempts. (See Figure 10.) Entry of PSC The least significant PSC byte beginning with the least significant bit must be entered first and then the most significant (see Table 1). If both PSC byte 1's and byte 2's comparisons prove correct, the memory erase/write access will be enabled and PSC may be changed as wished, except the corresponding protect bits are 0 (enabled). (See Figure 11.) Condition when supplied IS23SC4428 is supplied by the manufacturer with a 2-byte PSC (transport security code) which is determined in cooperation with the customer. RST I/O CLK E/W (internal signal) Command Entry Writing Error Counter Write 0 S0 D6 23 0 1 2 99 102 … D7 S1 Figure 10. Writing Error Counter |
Similar Part No. - IS23SC4428-X3 |
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Similar Description - IS23SC4428-X3 |
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