KM44H16030T-GZ View Datasheet(PDF) - Samsung

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KM44H16030T-GZ

DDR SDRAM Specification Version 0.61

Samsung 

128Mb DDR SDRAM

Target

3. For a Write with autoprecharge command, a new Bank Activate command may be issued to the same

bank after tWR+tRP where tWR+tRP starts on the falling DQS edge that strobed in the last valid data and

ends on the rising clock edge that strobes in the Bank Activate command. During write with

autoprecharge, the initiation of the internal precharge occurs at the same time as the earliest possible

external Precharge command without interrupting the Write burst as described in 1 above.

4. In all cases, a Precharge operation cannot be initiated unless tRAS(min) [minimum Bank Activate to

Precharge time] has been satisfied. This includes Write with autoprecharge commands where tRAS(min)

must still be satisfied such that a Write with autoprecharge command has the same timing as a Write

command followed by the earliest possible Precharge command which does not interrupt the burst.

3.3.9 Burst Stop

The burst stop command is initiated by having RAS and CAS high with CS and WE low at the rising edge of

the clock(CK). The burst stop command has the fewest restrictions making it the easiest method to use when

terminating a burst read operation before it has been completed. When the burst stop command is issued dur-

ing a burst read cycle, the pair of data and DQS(Data Strobe) go to a high impedance state after a delay which

is equal to the CAS latency set in the mode register. The burst stop command, however, is not supported dur-

ing a write burst operation.

< Burst Length=4, CAS Latency= 2, 2.5 >

0

1

2

3

4

5

6

7

CK

CK

Command READ A Burst Stop

NOP

NOP

NOP

NOP

NOP

NOP

CAS Latency=2

DQS

DQ ′s

The burst ends after a delay equal to the CAS latency.

Dout 0 Dout 1

CAS Latency=2.5

DQS

DQ ′s

Dout 0 Dout 1

8

NOP

Figure 17. Burst stop timing

The Burst Stop command is a mandatory feature for DDR SDRAMs. The following functionality is required:

1. The BST command may only be issued on the rising edge of the input clock, CK.

2. BST is only a valid command during Read bursts.

3. BST during a Write burst is undefined and shall not be used.

4. BST applies to all burst lengths.

5. BST is an undefined command during Read with autoprecharge and shall not be used.

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REV. 0.61 August 9. '99

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