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AM29BDD160G 数据表(PDF) 30 Page - Advanced Micro Devices |
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AM29BDD160G 数据表(HTML) 30 Page - Advanced Micro Devices |
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30 / 79 page ![]() 28 Am29BDD160G June 7, 2006 6. Executing the Chip Erase command is permitted when the SecSi sector is enabled. The Chip Erase command erases all sectors in the memory array except for sector 0 in top-bootblock configuration and sector 45 in bottom-bootblock configuration. The SecSi Sector is a one-time programmable memory area that cannot be erased. 7. Executing the SecSi Sector Entry command during program or erase suspend mode is allowed. The Sector Erase/Program Resume command is dis- abled while the SecSi sector is enabled, and the user cannot resume programming of the memory array until the Exit SecSi Sector command is writ- ten. SecSi Sector Protection Bit The SecSi Sector Protection Bit prevents program- ming of the SecSi sector memory area. Once set, the SecSi sector memory area contents are non-modifi- able. Persistent Protection Bit Lock The Persistent Protection Bit (PPB) Lock is a volatile bit that reflects the state of the Password Mode Lock- ing Bit after power-up reset. If the Password Mode Locking Bit is set, which indicates the device is in Password Protection Mode, the PPB Lock Bit is also set after a hardware reset (RESET# asserted) or a power-up reset. The ONLY means for clearing the PPB Lock Bit in Password Protection Mode is to issue the Password Unlock command. Successful execution of the Password Unlock command clears the PPB Lock Bit, allowing for sector PPBs modifications. As- serting RESET#, taking the device through a power-on reset, or issuing the PPB Lock Bit Set command sets the PPB Lock Bit back to a “1”. If the Password Mode Locking Bit is not set, indicating Persistent Sector Protection Mode, the PPB Lock Bit is cleared after power-up or hardware reset. The PPB Lock Bit is set by issuing the PPB Lock Bit Set com- mand. Once set the only means for clearing the PPB Lock Bit is by issuing a hardware or power-up reset. The Password Unlock command is ignored in Persis- tent Sector Protection Mode. Hardware Data Protection The command sequence requirement of unlock cycles for programming or erasing provides data protection against inadvertent writes. In addition, the following hardware data protection measures prevent accidental erasure or programming, which might otherwise be caused by spurious system level signals during V CC power-up and power-down transitions, or from system noise. Low V CC Write Inhibit When V CC is less than VLKO, the device does not ac- cept any write cycles. This protects data during V CC power-up and power-down. The command register and all internal erase/program circuits are disabled, and the device resets. Subsequent writes are ignored until V CC is greater than VLKO. The system must pro- vide the proper signals to the control pins to prevent unintentional writes when V CC 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 (VIL) while OE# is a logical one (VIH). Power-Up Write Inhibit If WE# = CE# = V IL and OE# = VIH during power-up, the device does not accept commands on the rising edge of WE#. The internal state machine is automati- cally reset to reading array data on power-up. VCC and VIO Power-up And Power-down Sequencing The device imposes no restrictions on V CC and VIO power-up or power-down sequencing. Asserting RE- SET# to V IL is required during the entire VCC and VIO power sequence until the respective supplies reach their operating voltages. Once, V CC and VIO attain their respective operating voltages, de-assertion of RE- SET# to V IH is permitted. |
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