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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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AM29BDS128H Fiches technique(PDF) 43 Page - Advanced Micro Devices |
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AM29BDS128H Fiches technique(HTML) 43 Page - Advanced Micro Devices |
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43 / 89 page  May 10, 2006 27024B3 Am29BDS128H/Am29BDS640H 41 D A TA SH EE T tection Mode Locking Bit is programmed. If not, the system must repeat this program sequence from the fourth cycle of “PL/68h”. Exiting the Persistent Protec- tion Mode Locking Bit Program command is accom- plished by writing the SecSi Sector Exit command or Reset command. SecSi Sector Protection Bit Program Command To protect the SecSi Sector, write the SecSi Sector Protect command sequence while in the SecSi Sector mode. After issuing “OPBP/48h” at the fourth bus cy- cle, the device requires a time out period of approxi- mately 150 µs to protect the SecSi Sector. Then, by writing “OPBP/48” at the fifth bus cycle, the device out- puts verify data at DQ0. If DQ0 = 1, then the SecSi Sector is protected. If not, then the system must re- peat this program sequence from the fourth cycle of “OPBP/48h”. PPB Lock Bit Set Command The PPB Lock Bit Set command is used to set the PPB Lock bit if it is cleared either at reset or if the Password Unlock command was successfully exe- cuted. There is no PPB Lock Bit Clear command. Once the PPB Lock Bit is set, it cannot be cleared un- less the device is taken through a power-on clear or the Password Unlock command is executed. Upon set- ting the PPB Lock Bit, the PPBs are latched into the DYBs. If the Password Mode Locking Bit is set, the PPB Lock Bit status is reflected as set, even after a power-on reset cycle. Exiting the PPB Lock Bit Set command is accomplished by writing the SecSi Sector Exit command, only while in the Persistent Sector Pro- tection Mode. DYB Write Command The DYB Write command is used to set or clear a DYB for a given sector. The high order address bits (Amax–A11) are issued at the same time as the code 01h or 00h on DQ7-DQ0. All other DQ data bus pins are ignored during the data write cycle. The DYBs are modifiable at any time, regardless of the state of the PPB or PPB Lock Bit. The DYBs are cleared at power-up or hardware reset. Exiting the DYB Write command is accomplished by writing the Read/Reset command. Password Unlock Command The Password Unlock command is used to clear the PPB Lock Bit so that the PPBs can be unlocked for modification, thereby allowing the PPBs to become ac- cessible for modification. The exact password must be entered in order for the unlocking function to occur. This command cannot be issued any faster than 2 µs at a time to prevent a hacker from running through the all 64-bit combinations in an attempt to correctly match a password. If the command is issued before the 2 µs execution window for each portion of the unlock, the command will be ignored. The Password Unlock function is accomplished by writing Password Unlock command and data to the de- vice to perform the clearing of the PPB Lock Bit. The password is 64 bits long, so the user must write the Password Unlock command 4 times. A1 and A0 are used for matching. Writing the Password Unlock com- mand is not address order specific. The lower address A1–A0= 00, the next Password Unlock command is to A1–A0= 01, then to A1–A0= 10, and finally to A1–A0= 11. Once the Password Unlock command is entered for all four words, the RDY pin goes LOW indicating that the device is busy. Approximately 1 µs is required for each portion of the unlock. Once the first portion of the password unlock completes (RDY is not driven and DQ6 does not toggle when read), the Password Un- lock command is issued again, only this time with the next part of the password. Four Password Unlock com- mands are required to successfully clear the PPB Lock Bit. As with the first Password Unlock command, the RDY signal goes LOW and reading the device re- sults in the DQ6 pin toggling on successive read oper- ations until complete. It is the responsibility of the microprocessor to keep track of the number of Pass- word Unlock commands, the order, and when to read the PPB Lock bit to confirm successful password un- lock. In order to relock the device into the Password Mode, the PPB Lock Bit Set command can be re-is- sued. Exiting the Password Unlock Command is ac- complished by writing SecSi Sector Exit command. |
Numéro de pièce similaire - AM29BDS128H |
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Description similaire - AM29BDS128H |
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