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2Gb: x4, x8, x16 DDR3 SDRAM - Micron

2Gb: x4, x8, x16 DDR3 SDRAM - Micron

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ACTIVATE Operation<br />

Before any READ or WRITE commands can be issued to a bank within the DRAM, a row<br />

in that bank must be opened (activated). This is accomplished via the ACTIVATE command,<br />

which selects both the bank and the row to be activated.<br />

After a row is opened with an ACTIVATE command, a READ or WRITE command may<br />

be issued to that row, subject to the tRCD specification. However, if the additive latency<br />

is programmed correctly, a READ or WRITE command may be issued prior to tRCD (MIN). In this operation, the DRAM enables a READ or WRITE command to be issued<br />

after the ACTIVATE command for that bank, but prior to tRCD (MIN) with the requirement<br />

that (ACTIVATE-to-READ/WRITE) + AL � tRCD (MIN) (see Posted CAS Additive<br />

Latency). tRCD (MIN) should be divided by the clock period and rounded up to the next<br />

whole number to determine the earliest clock edge after the ACTIVATE command on<br />

which a READ or WRITE command can be entered. The same procedure is used to convert<br />

other specification limits from time units to clock cycles.<br />

When at least one bank is open, any READ-to-READ command delay or WRITE-to-<br />

WRITE command delay is restricted to tCCD (MIN).<br />

A subsequent ACTIVATE command to a different row in the same bank can only be issued<br />

after the previous active row has been closed (precharged). The minimum time interval<br />

between successive ACTIVATE commands to the same bank is defined by tRC. A subsequent ACTIVATE command to another bank can be issued while the first bank is<br />

being accessed, which results in a reduction of total row-access overhead. The minimum<br />

time interval between successive ACTIVATE commands to different banks is defined<br />

by tRRD. No more than four bank ACTIVATE commands may be issued in a given<br />

tFAW (MIN) period, and the tRRD (MIN) restriction still applies. The tFAW (MIN) parameter<br />

applies, regardless of the number of banks already opened or closed.<br />

Figure 64: Example: Meeting t RRD (MIN) and t RCD (MIN)<br />

CK#<br />

CK<br />

Command<br />

Address<br />

BA[2:0]<br />

T0 T1<br />

T2 T3 T4 T5 T8 T9<br />

ACT NOP<br />

NOP ACT NOP<br />

NOP NOP NOP NOP<br />

RD/WR<br />

Row Row Col<br />

Bank x Bank y Bank y<br />

t RRD<br />

<strong>2Gb</strong>: <strong>x4</strong>, <strong>x8</strong>, <strong>x16</strong> <strong>DDR3</strong> <strong>SDRAM</strong><br />

ACTIVATE Operation<br />

t RCD<br />

Indicates break<br />

in time scale<br />

T10 T11<br />

Don’t Care<br />

PDF: 09005aef826aaadc<br />

<strong>2Gb</strong>_<strong>DDR3</strong>_<strong>SDRAM</strong>.pdf – Rev. P 2/12 EN 155 <strong>Micron</strong> Technology, Inc. reserves the right to change products or specifications without notice.<br />

� 2006 <strong>Micron</strong> Technology, Inc. All rights reserved.

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