IC61C6416 Datasheet, PDF(61/80 Page) Integrated Circuit Solution Inc – 64K X 16 HIGH-SPEED CMOS STATIC RAM

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IC61C6416 Datasheet, PDF (61/80 Pages) Integrated Circuit Solution Inc – 64K X 16 HIGH-SPEED CMOS STATIC RAM

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HYB18T256324Fâ[16/20/22]

256-Mbit DDR SGRAM

Functional Description

3.11

Auto Refresh Command (AREF)

#, +

#, +

#+ %

#3

2!3

#!3

7%

! !

"! "!

Figure 45

"! " AN K!D D RE SS

$O NgT# A RE

Auto Refresh Command

AREF is used to do a refresh cycle on one row in each

bank. The addresses are generated by an internal

refresh controller; external address pins are âDONâT

CAREâ. All banks must be idle before the AREF

command can be applied. The delay between the

AREF command and the next ACT or subsequent

AREF must be at least tRFC(min). The refresh period

starts when the AREF command is entered and ends

tRFC later at which time all banks will be in the idle state.

Within a period of tREF=32ms the whole memory has to

be refreshed. The average periodic interval time from

AREF to AREF is then tREFI(max)=7.8Âµs.

To improve efficiency bursts of AREF commands can

be used. Such bursts may consist of maximum 8 AREF

commands. tRFC(min) is the minimum required time

between two AREF commands inside one AREF burst.

According to the number of AREF commands in one

burst the average required time from one AREF burst

to the next can be increased. Example: If the AREF

bursts consists of 4 AREF commands, the average

time from one AREF burst to the next is 4 * 7.8Âµs =

31.2Âµs.

The AREF command generates an update of the OCD

output impedance and of the addresses, commands

and DQ terminations. The timing parameter tKO ( see

section 2.3.2 ) must be complied with.

#, +

#,+

#O MM AN D 02%

!2&

./ 0

!#

./0

!2&

./ 0

#+ %

T20

T2 &#

Figure 46 Auto Refresh Cycle

T2% & )

!#! 2% & O R!# 4 #O M MAN D

!2& ! U TO 2 E FRE SH

$O N gT# A RE

Table 28 Autorefresh Timing Parameters for â1.6, â2.0 and â2.2 speed sorts

Parameter

Symbol

Limit Values

Unit

â1.6

â2.0

â2.2

min max min max min max

Refresh Period (4096 cycles)

tREF

Average periodic Auto Refresh interval tREFI

Delay from AREF to next ACT/ AREF tRFC

â 32 â 32 â 32 ms

7.8

7.8

7.8

Âµs

54 â 54 â 54 â ns

Notes

Data Sheet

61

Rev. 1.11, 04-2005

10292004-DOXT-FS0U

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