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M29W641DU12ZA6F Datasheet(PDF) 11 Page - STMicroelectronics |
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M29W641DU12ZA6F Datasheet(HTML) 11 Page - STMicroelectronics |
11 / 42 page 11/42 M29W641DH, M29W641DL, M29W641DU COMMAND INTERFACE All Bus Write operations to the memory are inter- preted by the Command Interface. Commands consist of one or more sequential Bus Write oper- ations. Failure to observe a valid sequence of Bus Write operations will result in the memory return- ing to Read mode. The long command sequences are imposed to maximize data security. See Table 3 for a summary of the commands. Read/Reset Command The Read/Reset command returns the memory to its Read mode where it behaves like a ROM or EPROM. It also resets the errors in the Status Register. Either one or three Bus Write operations can be used to issue the Read/Reset command. The Read/Reset command can be issued, be- tween Bus Write cycles before the start of a pro- gram or erase operation, to return the device to read mode. If the Read/Reset command is issued during the timeout of a Block erase operation then the memory will take up to 10µs to abort. During the abort period no valid data can be read from the memory. The Read/Reset command will not abort an Erase operation when issued while in Erase Suspend. Auto Select Command The Auto Select command is used to read the Manufacturer Code, the Device Code, the Block Protection Status and the Extended Memory Block Verify Code. Three consecutive Bus Write opera- tions are required to issue the Auto Select com- mand. Once the Auto Select command is issued the memory remains in Auto Select mode until a Read/Reset command is issued. Read CFI Query and Read/Reset commands are accepted in Auto Select mode, all other commands are ignored. In Auto Select mode the Manufacturer Code can be read using a Bus Read operation with A0 = VIL and A1 = VIL. The other address bits may be set to either VIL or VIH. The Manufacturer Code for ST- Microelectronics is 0020h. The Device Code can be read using a Bus Read operation with A0 = VIH and A1 = VIL. The other address bits may be set to either VIL or VIH. The Device Code for the M29W641D is 22C7h. The Block Protection Status of each block can be read using a Bus Read operation with A0 = VIL, A1 = VIH, and A12-A21 specifying the address of the block. The other address bits may be set to ei- ther VIL or VIH. If the addressed block is protected then 01h is output on Data Inputs/Outputs DQ0- DQ7, otherwise 00h is output. Read CFI Query Command The Read CFI Query Command is used to read data from the Common Flash Interface (CFI) Memory Area. This command is valid when the de- vice is in the Read Array mode, or when the device is in Autoselected mode. One Bus Write cycle is required to issue the Read CFI Query Command. Once the command is is- sued subsequent Bus Read operations read from the Common Flash Interface Memory Area. The Read/Reset command must be issued to re- turn the device to the previous mode (the Read Ar- ray mode or Autoselected mode). A second Read/ Reset command would be needed if the device is to be put in the Read Array mode from Autoselect- ed mode. See Appendix B, Table 18 to Table 23 for details on the information contained in the Common Flash Interface (CFI) memory area. Program Command The Program command can be used to program a value to one address in the memory array at a time. The command requires four Bus Write oper- ations, the final write operation latches the ad- dress and data, and starts the Program/Erase Controller. If the address falls in a protected block then the Program command is ignored, the data remains unchanged. The Status Register is never read and no error condition is given. During the program operation the memory will ig- nore all commands. It is not possible to issue any command to abort or pause the operation. Typical program times are given in Table 4. Bus Read op- erations during the program operation will output the Status Register on the Data Inputs/Outputs. See the section on the Status Register for more details. After the program operation has completed the memory will return to the Read mode, unless an error has occurred. When an error occurs the memory will continue to output the Status Regis- ter. A Read/Reset command must be issued to re- set the error condition and return to Read mode. Note that the Program command cannot change a bit set at ’0’ back to ’1’. One of the Erase Com- mands must be used to set all the bits in a block or in the whole memory from ’0’ to ’1’. Fast Program Commands There is a Fast Program command available to im- prove the programming throughput, by writing sev- eral adjacent words or bytes in parallel: the Double Word Program command. Double Word Program Command. The Double Word Program command is used to write a page of two adjacent words in parallel. The two words must differ only for the address A0. Three bus write cycles are necessary to issue the Double Word Program command. |
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