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W3E32M72S-333SBI Datasheet(PDF) 6 Page - White Electronic Designs Corporation |
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W3E32M72S-333SBI Datasheet(HTML) 6 Page - White Electronic Designs Corporation |
6 / 19 page W3E32M72S-XSBX 6 White Electronic Designs Corporation • (602) 437-1520 • www.wedc.com White Electronic Designs July 2006 Rev. 6 White Electronic Designs Corp. reserves the right to change products or specifications without notice. device loses power. The enabling of the DLL should always be followed by a LOAD MODE REGISTER command to the mode register (BA0/BA1 both LOW) to reset the DLL. The extended mode register must be loaded when all banks are idle and no bursts are in progress, and the controller must wait the specified time before initiating any subsequent operation. Violating either of these requirements could result in unspecified operation. OUTPUT DRIVE STRENGTH The normal full drive strength for all outputs are specified to be SSTL2, Class II. The DDR SDRAM supports an option for reduced drive. This option is intended for the support of the lighter load and/or point-to-point environments. The selection of the reduced drive strength will alter the DQs and DQSs from SSTL2, Class II drive strength to a reduced drive strength, which is approximately 54 percent of the SSTL2, Class II drive strength. DLL ENABLE/DISABLE When the part is running without the DLL enabled, device functionality may be altered. The DLL must be enabled for normal operation. DLL enable is required during power- up initialization and upon returning to normal operation after having disabled the DLL for the purpose of debug or evaluation. (When the device exits self refresh mode, the DLL is enabled automatically.) Any time the DLL is enabled, 200 clock cycles with CKE high must occur before a READ command can be issued. ALLOWABLE OPERATING FREQUENCY (MHz) SPEED CAS LATENCY = 2 CAS LATENCY = 2.5 -200 ≤ 75 ≤ 100 -250 ≤ 100 ≤ 125 -266 ≤ 100 ≤ 133 -333 - ≤ 166 TABLE 2 - CAS LATENCY COMMANDS The Truth Table provides a quick reference of available commands. This is followed by a written description of each command. DESELECT The DESELECT function (CS# High) prevents new commands from being executed by the DDR SDRAM. The SDRAM is effectively deselected. Operations already in progress are not affected. NO OPERATION (NOP) The NO OPERATION (NOP) command is used to perform a NOP to the selected DDR SDRAM (CS# is LOW while RAS#, CAS#, and WE# are high). This prevents unwanted commands from being registered during idle or wait states. Operations already in progress are not affected. LOAD MODE REGISTER The Mode Registers are loaded via inputs A0-12. The LOAD MODE REGISTER command can only be issued when all banks are idle, and a subsequent executable command cannot be issued until tMRD is met. ACTIVE The ACTIVE command is used to open (or activate) a row in a particular bank for a subsequent access. The value on the BA0, BA1 inputs selects the bank, and the address provided on inputs A0-12 selects the row. This row remains active (or open) for accesses until a PRECHARGE command is issued to that bank. A PRECHARGE command must be issued before opening a different row in the same bank. READ The READ command is used to initiate a burst read access to an active row. The value on the BA0, BA1 inputs selects the bank, and the address provided on inputs A0-9 selects the starting column location. The value on input A10 determines whether or not AUTO PRECHARGE is used. If AUTO PRECHARGE is selected, the row being accessed will be precharged at the end of the READ burst; if AUTO PRECHARGE is not selected, the row will remain open for subsequent accesses. |
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