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M27W016 数据表(PDF) 9 Page - STMicroelectronics |
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M27W016 数据表(HTML) 9 Page - STMicroelectronics |
9 / 26 page 9/26 M27W016 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. Refer to Tables 3 and 4, for a summary of the com- mands. Read/Reset Command. The Read/Reset command returns the memory to its Read mode where it behaves like a ROM or EPROM, unless otherwise stated. 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. VPP must be set to VHH during the Read/Reset command. If VPP is set to either VIL or VIH the com- mand will be ignored. The command can be is- sued, between Bus Write cycles before the start of a program operation, to return the device to read mode. Once the program operation has started the Read/Reset command is no longer accepted. Auto Select Command. The Auto Select command is used to read the Manufacturer Code and the Device Code. VPP must be set to VHH during the Auto Select com- mand. If VPP is set to either VIL or VIH the com- mand will be ignored. Three consecutive Bus Write operations are required to issue the Auto Se- lect command. Once the Auto Select command is issued the memory remains in Auto Select mode until a Read/Reset command is issued, all other commands are ignored. From the 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 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. Word Program Command. The Word Program command can be used to pro- gram a Word to the memory array. VPP must be set to VHH during Word Program. If VPP is set to ei- ther VIL or VIH the command will be ignored, the data will remain unchanged and the device will re- vert to Read/Reset mode. The command requires four Bus Write operations, the final write operation latches the address and data in the internal state machine and starts the PC. 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 5. 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’. Multiple Word Program Command The Multiple Word Program command can be used to program large streams of data. It greatly reduces the total programming time when a large number of Words are written in the memory at once. VPP must be set to VHH during Multiple Word Program. If VPP is set either VIL or VIH the com- mand will be ignored, the data will remain un- changed and the device will revert to Read mode. It has four phases: the Setup Phase to initiate the command, the Program Phase to program the data to the memory, the Verify Phase to check that the data has been correctly programmed and re- program if necessary and the Exit Phase. Setup Phase. The Multiple Word Program com- mand requires three Bus Write operations to ini- tiate the command (refer to Table 4, Multiple Word Program Command and Figure 8, Multiple Word Program Flowchart). The Status Register must be read in order to check that the PC has started (see Table 6 and Figure 8). Program Phase. The Program Phase requires n+1 Bus Write operations, where n is the number of Words, to execute the programming phase (re- fer to Table 4, Multiple Word Program and Figure 7, Multiple Word Program Flowchart). Before any Bus Write operation of the Program Phase, the Status Register must be read in order to check that the PC is ready to accept the opera- tion (see Table 6 and Figure 8). The Program Phase is executed in three different sub-phases: 1. The first Bus Write operation of the Program Phase (the 4th of the command) latches the Start Address and the first Word to be programmed. 2. Each subsequent Bus Write operation latches the next Word to be programmed and automatically increments the internal Address Bus. It is not necessary to provide the address of the location to be programmed but only a Continue Address, CA (A17 to A19 equal to the |
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类似说明 - M27W016 |
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