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AM49PDL127BH Datasheet(PDF) 52 Page - SPANSION |
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AM49PDL127BH Datasheet(HTML) 52 Page - SPANSION |
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52 / 86 page  50 Am49PDL127BH/Am49PDL129BH December 16, 2003 ADV ANCE I N FO RMAT I O N word program command, and all the password data. There is no special addressing order required for pro- gramming the password. Also, when the password is undergoing programming, Simultaneous Operation is disabled. Read operations to any memory location will return the programming status. Once programming is complete, the user must issue a Read/Reset com- mand to return the device to normal operation. Once the Password is written and verified, the Password Mode Locking Bit must be set in order to prevent verifi- cation. The Password Program Command is only ca- pable of programming “0”s. Programming a “1” after a cell is programmed as a “0” results in a time-out by the Embedded Program Algorithm™ with the cell remain- ing as a “0”. The password is all ones when shipped from the factory. All 64-bit password combinations are valid as a password. Password Verify Command The Password Verify Command is used to verify the Password. The Password is verifiable only when the Password Mode Locking Bit is not programmed. If the Password Mode Locking Bit is programmed and the user attempts to verify the Password, the device will al- ways drive all F’s onto the DQ data bus. The Password Verify command is permitted if the SecSi sector is enabled. Also, the device will not oper- ate in Simultaneous Operation when the Password Verify command is executed. Only the password is re- turned regardless of the bank address. The lower two address bits (A1-A0) are valid during the Password Verify. Writing the Read/Reset command returns the device back to normal operation. Password Protection Mode Locking Bit Program Command The Password Protection Mode Locking Bit Program Command programs the Password Protection Mode Locking Bit, which prevents further verifies or updates to the Password. Once programmed, the Password Protection Mode Locking Bit cannot be erased! If the Password Protection Mode Locking Bit is verified as program without margin, the Password Protection Mode Locking Bit Program command can be executed to improve the program margin. Once the Password Protection Mode Locking Bit is programmed, the Per- sistent Sector Protection Locking Bit program circuitry is disabled, thereby forcing the device to remain in the Password Protection mode. Exiting the Mode Locking Bit Program command is accomplished by writing the Read/Reset command. Persistent Sector Protection Mode Locking Bit Program Command The Persistent Sector Protection Mode Locking Bit Program Command programs the Persistent Sector Protection Mode Locking Bit, which prevents the Pass- word Mode Locking Bit from ever being programmed. If the Persistent Sector Protection Mode Locking Bit is verified as programmed without margin, the Persistent Sector Protection Mode Locking Bit Program Com- mand should be reissued to improve program margin. By disabling the program circuitry of the Password Mode Locking Bit, the device is forced to remain in the Persistent Sector Protection mode of operation, once this bit is set. Exiting the Persistent Protection Mode Locking Bit Program command is accomplished by writing the Read/Reset command. SecSi Sector Protection Bit Program Command The SecSi Sector Protection Bit Program Command programs the SecSi Sector Protection Bit, which pre- vents the SecSi sector memory from being cleared. If the SecSi Sector Protection Bit is verified as pro- grammed without margin, the SecSi Sector Protection Bit Program Command should be reissued to improve program margin. Exiting the V CC-level SecSi Sector Protection Bit Program Command is accomplished by writing the Read/Reset command. 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 Read/Reset command (only in the Persistent Protection 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 A22–A12 for PDL127 and A21–A12 for PDL129H are issued at the same time as the code 01h or 00h on DQ7-DQ0. All other DQ data bus pins are ignored dur- ing 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 hard- ware reset. Exiting the DYB Write command is accom- plished 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- |
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