CMS3216LAH datasheet(39/46 Pages) FIDELIX

39 / 46 page

Rev0.2, Aug. 2006

CMS3216LAx-75Ex

Concurrent Auto Precharge

If an access command with Auto Precharge is being execeuted

an access command (either a Read or Write ) is not allowed by

SDRAM’s. If this feature is allowed then the SDRAM supports

Concurrent

Auto

Precharge.

Fidelix

SDRAMs

support

Concurrent Auto Precharge. Four casees where Concurrent

Auto Precharge occurs are defined below.

Read With Auto Precharge

1.Interrupted by a Read(with or without auto precharge): A read

to bank m will interrupt a Read on bank n, CAS latency later.

The precharge to bank n will begin when the Read to bank m is

registered. (Figure 25. )

2. Interrupted by a Write(with or without auto precharge): A

Write to bank m will interrupt a Read on bank n when registered.

DQM should be used two clocks prior to the Write command to

prevent bus contention. The Precharge to bank n will begin

when the write to bank m is registered. (Figure 26. )

Write with Auto Precharge

3. Interrupted by a Read(with or without auto precharge): A

Read to bank m will interrupt a Write on bank n when regis-

tered , with the data-out appearing CAS latency later. The Pre-

charge to bank n will begin after tWR is met, where tWR begins

when the Read to bank m is registered. The last valid Write to

bank n will be data-in registered one clock prior to the Read to

bank m.(Figure 27. )

4. Interrupted by a Write ( with or without auto Precharge): A

Write to bank m will interrupt a Write on bank n when registered.

The Precharge to bank n will begin after tWR is met ,where tWR

begins when the Write to bank m is registered. The latest valid

data Write to bank n will be data registered one clock prior to a

Write to bank m.( Figure 28. )

Figure 24. Clock Suspend During Read Burst - Burst of 4 (CAS latency =2)

CLK

Command

Address

Read

NOP

CKE

NOP

Internal

CLK

Bank

Col n

Dout

n+1

Dout

n+2

NOP

Dout

n+3

Dout

NOP

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