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AM29LV081B Datasheet(PDF) 15 Page - Advanced Micro Devices |
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AM29LV081B Datasheet(HTML) 15 Page - Advanced Micro Devices |
15 / 40 page 21525D6 October 12, 2006 Am29LV081B 13 D A TA SH EE T quence should be reinitiated once the device has reset to reading array data, to ensure data integrity. Programming is allowed in any sequence and across sector boundaries. A bit cannot be programmed from a “0” back to a “1”. Attempting to do so may halt the operation and set DQ5 to “1”, or cause the Data# Polling algorithm to indicate the operation was suc- cessful. However, a succeeding read will show that the data is still “0”. Only erase operations can convert a “0” to a “1”. Unlock Bypass Command Sequence The unlock bypass feature allows the system to pro- gram bytes to the device faster than using the standard program command sequence. The unlock bypass com- mand sequence is initiated by first writing two unlock cycles. This is followed by a third write cycle containing the unlock bypass command, 20h. The device then en- ters the unlock bypass mode. A two-cycle unlock by- pass program command sequence is all that is required to program in this mode. The first cycle in this se- quence contains the unlock bypass program com- mand, A0h; the second cycle contains the program address and data. Additional data is programmed in the same manner. This mode dispenses with the initial two unlock cycles required in the standard program command sequence, resulting in faster total program- ming time. Table 4 shows the requirements for the com- mand sequence. During the unlock bypass mode, only the Unlock By- pass Program and Unlock Bypass Reset commands are valid. To exit the unlock bypass mode, the system must issue the two-cycle unlock bypass reset com- mand sequence. The first cycle must contain the data 90h; the second cycle the data 00h. The device then re- turns to reading array data. Figure 3 illustrates the algorithm for the program oper- ation. See the Erase/Program Operations table in “AC Characteristics” for parameters, and to Figure 15 for timing diagrams. Chip Erase Command Sequence Chip erase is a six bus cycle operation. The chip erase command sequence is initiated by writing two unlock cycles, followed by a set-up command. Two additional unlock write cycles are then followed by the chip erase command, which in turn invokes the Embedded Erase algorithm. The device does not require the system to preprogram prior to erase. The Embedded Erase algo- rithm automatically preprograms and verifies the entire memory for an all zero data pattern prior to electrical erase. The system is not required to provide any con- trols or timings during these operations. Table 4 shows the address and data requirements for the chip erase command sequence. Any commands written to the chip during the Embed- ded Erase algorithm are ignored. Note that a hardware reset during the chip erase operation immediately ter- minates the operation. The Chip Erase command se- quence should be reinitiated once the device has returned to reading array data, to ensure data integrity. The system can determine the status of the erase op- eration by using DQ7, DQ6, DQ2, or RY/BY#. See “Write Operation Status” for information on these sta- tus bits. When the Embedded Erase algorithm is com- plete, the device returns to reading array data and addresses are no longer latched. Figure 4 illustrates the algorithm for the erase opera- tion. See the Erase/Program Operations tables in “AC Characteristics” for parameters, and to Figure 16 for timing diagrams. Sector Erase Command Sequence Sector erase is a six bus cycle operation. The sector erase command sequence is initiated by writing two un- lock cycles, followed by a set-up command. Two addi- tional unlock write cycles are then followed by the address of the sector to be erased, and the sector START Write Program Command Sequence Data Poll from System Verify Data? No Yes Last Address? No Yes Programming Completed Increment Address Embedded Program algorithm in progress Note: See Table 4 for program command sequence. Figure 3. Program Operation |
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