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IS42S16800A-6T Datasheet(PDF) 7 Page - Integrated Silicon Solution, Inc |
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IS42S16800A-6T Datasheet(HTML) 7 Page - Integrated Silicon Solution, Inc |
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7 / 61 page  Integrated Silicon Solution, Inc. — www.issi.com — 1-800-379-4774 7 PRELIMINARYINFORMATION Rev. 00C 01/20/05 ISSI® IS42S81600A, IS42S16800A, IS42S32400A GENERAL DESCRIPTION READ The READ command selects the bank from BA0, BA1 inputs and starts a burst read access to an active row. Inputs A0-A9 (x8); A0-A8 (x16); A0-A7 (x32) provides the starting column location. When A10 is HIGH, this command functions as an AUTO PRECHARGE command. When the auto precharge is selected, the row being accessed will be precharged at the end of the READ burst. The row will remain open for subsequent accesses when AUTO PRECHARGE is not selected. DQ’s read data is subject to the logic level on the DQM inputs two clocks earlier. When a given DQM signal was registered HIGH, the correspond- ing DQ’s will be High-Z two clocks later. DQ’s will provide valid data when the DQM signal was registered LOW. WRITE A burst write access to an active row is initiated with the WRITE command. BA0, BA1 inputs selects the bank, and the starting column location is provided by inputs A0-A9 (x8); A0-A8 (x16); A0-A7 (x32). Whether or not AUTO- PRECHARGE is used is determined by A10. The row being accessed will be precharged at the end of the WRITE burst, if AUTO PRECHARGE is selected. If AUTO PRECHARGE is not selected, the row will remain open for subsequent accesses. A memory array is written with corresponding input data on DQ’s and DQM input logic level appearing at the same time. Data will be written to memory when DQM signal is LOW. When DQM is HIGH, the corresponding data inputs will be ignored, and a WRITE will not be executed to that byte/ column location. PRECHARGE The PRECHARGE command is used to deactivate the open row in a particular bank or the open row in all banks. BA0, BA1 can be used to select which bank is precharged or they are treated as “Don’t Care”. A10 determined whether one or all banks are precharged. After executing this command, the next command for the selected banks(s) is executed after passage of the period t RP, which is the period required for bank precharging. Once a bank has been precharged, it is in the idle state and must be activated prior to any READ or WRITE commands being issued to that bank. AUTO PRECHARGE TheAUTOPRECHARGEfunctionensuresthattheprecharge is initiated at the earliest valid stage within a burst. This function allows for individual-bank precharge without requir- ing an explicit command. A10 to enable the AUTO PRECHARGE function in conjunction with a specific READ or WRITE command. For each individual READ or WRITE command, auto precharge is either enabled or disabled. AUTO PRECHARGE does not apply except in full-page burst mode. Upon completion of the READ or WRITE burst, a precharge of the bank/row that is addressed is automati- cally performed. AUTO REFRESH COMMAND This command executes the AUTO REFRESH operation. The row address and bank to be refreshed are automatically generated during this operation. The stipulated period (tRC) is required for a single refresh operation, and no other com- mands can be executed during this period. This command is executed at least 4096 times for every 64ms. During an AUTO REFRESH command, address bits are “Don’t Care”. This command corresponds to CBR Auto-refresh. BURST TERMINATE The BURST TERMINATE command forcibly terminates the burst read and write operations by truncating either fixed- length or full-page bursts and the most recently registered READ or WRITE command prior to the BURST TERMI- NATE. COMMAND INHIBIT COMMAND INHIBIT prevents new commands from being executed. Operations in progress are not affected, apart from whether the CLK signal is enabled NO OPERATION When CS is low, the NOP command prevents unwanted commands from being registered during idle or wait states. LOAD MODE REGISTER During the LOAD MODE REGISTER command the mode register is loaded from A0-A11. This command can only be issued when all banks are idle. ACTIVE COMMAND When the ACTIVE COMMAND is activated, BA0, BA1 inputs selects a bank to be accessed, and the address inputs on A0-A11 selects the row. Until a PRECHARGE command is issued to the bank, the row remains open for accesses. |
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