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AM29LV800DB-120ED Datasheet(PDF) 19 Page - Advanced Micro Devices |
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AM29LV800DB-120ED Datasheet(HTML) 19 Page - Advanced Micro Devices |
19 / 51 page January 21, 2005 Am29LV800D_00_A4_E Am29LV800D 17 P R E L I M I NARY Hardware Data Protection The command sequence requirement of unlock cycles for programming or erasing provides data protection against inadvertent writes (refer to Table 5 for command definitions). In addition, the following hardware data protection mea- sures prevent accidental erasure or program- ming, which might otherwise be caused by spurious 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 accept any write cycles. This protects data during VCC power-up and power-down. The co mm a nd r egis ter a nd a ll inter na l pr o- gram/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 unintentional 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 com- mands on the rising edge of WE#. The internal state machine is automatically reset to reading array data on power-up. Command Definitions Writing specific address and data commands or sequences into the command register initiates device operations. Table 5 defines the valid reg- ister command sequences. Writing incorrect address and data values or writing them in the improper sequence resets the device to reading array data. All addresses are latched on the falling edge of WE# or CE#, whichever happens later. All data is latched on the rising edge of WE# or CE#, whichever happens first. Refer to the appro- priate timing diagrams in the “AC Characteris- tics” section. Reading Array Data The device is automatically set to reading array data after device power-up. No commands are required to retrieve data. The device is also ready to read array data after completing an Embedded Program or Embedded Erase algo- rithm. After the device accepts an Erase Suspend com- mand, the device enters the Erase Suspend mode. The system can read array data using the standard read timings, except that if it reads at an address within erase-suspended sectors, the device outputs status data. After completing a programming operation in the Erase Suspend mode, the system may once again read array data with the same exception. See “Erase Sus- pend/Erase Resume Commands” for more infor- mation on this mode. The system must issue the reset command to re-enable the device for reading array data if DQ5 goes high, or while in the autoselect mode. See the “Reset Command” section, next. See also “Requirements for Reading Array Data” in the “Device Bus Operations” section for more information. The Read Operations table provides the read parameters, and Figure 1 shows the timing diagram. Reset Command Writing the reset command to the device resets the device to reading array data. Address bits are don’t care for this command. The reset command may be written between the sequence cycles in an erase command sequence before erasing begins. This resets the device to reading array data. Once erasure begins, how- ever, the device ignores reset commands until the operation is complete. The reset command may be written between the sequence cycles in a program command sequence before programming begins. This resets the device to reading array data (also applies to programming in Erase Suspend mode). Once programming begins, however, the device ignores reset commands until the opera- tion is complete. The reset command may be written between the sequence cycles in an autoselect command sequence. Once in the autoselect mode, the reset command must be written to return to reading array data (also applies to autoselect during Erase Suspend). |
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