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AS4LC2M8S1-7TC Datasheet(PDF) 10 Page - Alliance Semiconductor Corporation |
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AS4LC2M8S1-7TC Datasheet(HTML) 10 Page - Alliance Semiconductor Corporation |
10 / 29 page ® 5/21/01; v.1.1 Alliance Semiconductor P. 10 of 29 AS4LC2M8S1 AS4LC1M16S1 18 A proper power-up initialization sequence (as described on page 10) is needed before proper device operation is ensured. (VDD and VDDQ must be powered up simultaneously. VSS and VSSQ must be at the same potential.)Two AUTOREFRESH command wake-ups should be repeated any time the tREF refresh requirement is exceeded. 19 AC characteristics assume tT = 1 ns. 20 In addition to meeting the transition rate specification, the clock and CKE must transit between VIH and VIL (or between VIL and VIH) in a monotonic manner. 21 AC timing and IDD tests have VIL = 0V and VIH = 3.0 V with timing referenced to 1.4V crossover point. 22 IDD specifications are tested after the device is properly initialized. 23 Minimum clock cycles = (minimum time/clock cycle time) rounded up. Device operation Command Pin settings Description Power up The following sequence is recommended prior to normal operation. 1 Apply power, start clock, and assert CKE and DQM high. All other signals are NOP. 2 After power-up, pause for a minimum of 200µs. CKE/DQM = high; all others NOP. 3Precharge both banks. 4 Perform Mode Register Set command to initialize mode register. 5 Perform a minimum of 8 auto refresh cycles to stabilize internal circuitry. (Steps 4 and 5 may be interchanged.) Mode register set CS = RAS = CAS = WE = low; A0~A11 = opcode The mode register stores the user selected opcode for the SDRAM operating modes. The CAS latency, burst length, burst type, test mode and other vendor specific functions are selected/programmed during the Mode Register Set command cycle. The default setting of the mode register is not defined after power-up. Therefore, it is recommended that the power-up and mode register set cycle be executed prior to normal SDRAM operation. Refer to the Mode Register Set table and timing for details. Device deselect and no operation CS = high, or RAS, CAS, WE = high The SDRAM performs a “no operation” (NOP) when RAS, CAS, and WE = high. Since the NOP performs no operation, it may be used as a wait state in performing normal SDRAM functions. The SDRAM is deselected when CS is high. CS high disables the command decoder such that RAS, CAS, WE and address inputs are ignored. Device deselection is also considered a NOP. Bank activation CS = RAS = low; CAS = WE = high; A0~A10 = row address; A11 = bank select The SDRAM is configured with two internal banks. Use the Bank Activate command to select a row in one of the two idle banks. Initiate a read or write operation after tRCD(min) from the time of bank activation. Burst read CS = CAS = A10 = low; RAS = WE = high; A11 = bank select, A0~A8 = column address; (A9 = don’t care for 2M × 8; A8, A9 = don’t care for 1M × 16) Use the Burst Read command to access a consecutive burst of data from an active row in an active bank. Burst read can be initiated on any column address of an active row. The burst length, sequence and latency are determined by the mode register setting. The first output data appears after the CAS latency from the read command. The output goes into a high impedance state at the end of the burst (BL = 1,2,4,8) unless a new burst read is initiated to form a gapless output data stream. A full-page burst does not terminate automatically at the end of the burst. Terminate the burst with a burst stop command, precharge command to the same bank or another burst read/write |
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