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AS4C16M16SA-6TIN Datasheet(PDF) 8 Page - Alliance Semiconductor Corporation |
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AS4C16M16SA-6TIN Datasheet(HTML) 8 Page - Alliance Semiconductor Corporation |
8 / 55 page AS4C16M16SA-C&I Confidential 7 Rev. 3.0 Mar. /2015 Commands 1 BankActivate (RAS# = "L", CAS# = "H", WE# = "H", BAs = Bank, A0-A12 = Row Address) The BankActivate command activates the idle bank designated by the BA0, 1 signals. By latching the row address on A0 to A12 at the time of this command, the selected row access is initiated. The read or write operation in the same bank can occur after a time delay of tRCD(min.) from the time of bank activation. A subsequent BankActivate command to a different row in the same bank can only be issued after the previous active row has been precharged (refer to the following figure). The minimum time interval between successive BankActivate commands to the same bank is defined by tRC(min.). The SDRAM has four internal banks on the same chip and shares part of the internal circuitry to reduce chip area; therefore it restricts the back-to-back activation of the two banks. tRRD(min.) specifies the minimum time required between activating different banks. After this command is used, the Write command and the Block Write command perform the no mask write operation. CLK COMMAND T0 T1 ADDRESS T2 T3 Tn+3 Tn+4 Tn+5 Tn+6 RAS# - CAS# delay(tRCD) RAS# - RAS# delay time(tRRD) RAS# - Cycle time(tRC) AutoPrecharge Begin Bank A Row Addr. Bank A Col Addr. Bank B Row Addr. Bank A Row Addr. Bank A Activate NOP NOP R/W A with AutoPrecharge Bank B Activate NOP NOP Bank A Activate Don’t Care Figure 3. BankActivate Command Cycle (Burst Length = n) 2 BankPrecharge command (RAS# = "L", CAS# = "H", WE# = "L", BAs = Bank, A10 = "L", A0-A9, A11 and A12 = Don't care) The BankPrecharge command precharges the bank designated by BA signal. The precharged bank is switched from the active state to the idle state. This command can be asserted anytime after tRAS(min.) is satisfied from the BankActivate command in the desired bank. The maximum time any bank can be active is specified by tRAS(max.). Therefore, the precharge function must be performed in any active bank within tRAS(max.). At the end of precharge, the precharged bank is still in the idle state and is ready to be activated again. 3 PrechargeAll command (RAS# = "L", CAS# = "H", WE# = "L", BAs = Don’t care, A10 = "H", A0-A9, A11 and A12 = Don't care) The PrechargeAll command precharges all banks simultaneously and can be issued even if all banks are not in the active state. All banks are then switched to the idle state. 4 Read command (RAS# = "H", CAS# = "L", WE# = "H", BAs = Bank, A10 = "L", A0-A8 = Column Address) The Read command is used to read a burst of data on consecutive clock cycles from an active row in an active bank. The bank must be active for at least tRCD(min.) before the Read command is issued. During read bursts, the valid data-out element from the starting column address will be available following the CAS latency after the issue of the Read command. Each subsequent data-out element will be valid by the next positive clock edge (refer to the following figure). The DQs go into high-impedance at the end of the burst unless other command is initiated. The burst length, burst sequence, and CAS latency are determined by the mode register, which is already programmed. A full-page burst will continue until terminated (at the end of the page it will wrap to column 0 and continue). |
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