K4N56163QF Datasheet, PDF(57/73 Page) Samsung semiconductor

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K4N56163QF Datasheet, PDF (57/73 Pages) Samsung semiconductor – 256Mbit gDDR2 SDRAM

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K4N56163QF-GC

256M gDDR2 SDRAM

Precharge & Auto Precharge Clarification

From Command

Read w/AP

Write w/AP

Precharge

Precharge All

To Command

Precharge ( to same Bank as Read w/AP)

Precharge All

Precharge ( to same Bank as Write w/AP)

Precharge All

Precharge ( to same Bank as Precharge)

Precharge All

Precharge

Precharge All

Minimum Delay beweenâFrom Com-

mandâ to âTo Commandâ

AL + BL/2 + tRTP - 2 * tCK

WL + BL/2 + WR

1 * tCK

Unit Notes

clks 1, 2

clks

Notes:

1. The value of tRTP is decided by the equation : max( RU<tRTP/tCK>, 2) where RU stands for round up. This is required

to cover the max tCK case, which is 8 ns.

2. For a given bank, the precharge period of tRP should be counted from the latest precharge command issued to that

bank. Similarly, the precharge period of tRPall should be counted from the latest precharge all command ossued to the

DRAM.

2.2.7 Refresh Command

When CS, RAS and CAS are held low and WE high at the rising edge of the clock, the chip enters the Refresh mode

(REF). All banks of the gDDR2 SDRAM must be precharged and idle for a minimum of the Precharge time (tRP) before the

Refresh command (REF) can be applied. An address counter, internal to the device, supplies the bank address during the

refresh cycle. No control of the external address bus is required once this cycle has started.

When the refresh cycle has completed, all banks of the gDDR2 SDRAM will be in the precharged (idle) state. A delay

between the Refresh command (REF) and the next Activate command or subsequent Refresh command must be greater

than or equal to the Refresh cycle time (tRFC).

To allow for improved efficiency in scheduling and switching between tasks, some flexibility in the absolute refresh interval

is provided. A maximum of eight Refresh commands can be posted to any given gDDR2 SDRAM, meaning that the maxi-

mum absolute interval between any Refresh command and the next Refresh command is 9 * tREFI.

CK/CK

CKE

High

> = tRP

CMD Precharge

NOP

> = tRFC

REF

Tn + 1

> = tRFC

NOP

ANY

- 57 -

Rev 1.6 (Apr. 2005)

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