T4312816B 查看數據表（PDF） - Taiwan Memory Technology

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T4312816B

8M x 16 SDRAM 2M x 16bit x 4Banks Synchronous DRAM

Taiwan Memory Technology 

tm TE

CH

T4312816B

Commands

1 BankActivate

(RAS# = "L", CAS# = "H", WE# = "H", BAs = Bank, A0-A11 = Row Address)

The BankActivate command activates the idle bank designated by the BA0,1 signals. By latching the row

address on A0 to A11 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 four 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.

T0

T1

T2

T3

Tn+3

Tn+4

Tn+5

Tn+6

CLK

..............

ADDRESS

COMMAND

Bank A

Row Addr.

RAS# - CAS# delay (tRCD)

Bank A

Activate

NOP

NOP

Bank A

Col Addr.

..............

Bank B

Row Addr.

Bank A

Row Addr.

RAS# - RAS# delay time (tRRD)

R/W A with

AutoPrecharge

..............

RAS# Cycle time (tRC)

Bank B

Activate

NOP

NOP

Bank A

Activate

: "H" or "L"

AutoPrecharge

Begin

BankActivate Command Cycle (Burst Length = n, CAS# Latency = 3)

2 BankPrecharge command

(RAS# = "L", CAS# = "H", WE# = "L", BAs = Bank, A10 = "L", A0-A9 and A11 = Don't care)

The BankPrecharge command precharges the bank disignated 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 and A11 = 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).

TM Technology Inc. reserves the right

P. 5

to change products or specifications without notice.

Publication Date: FEB. 2007

Revision: A

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