Integrated Silicon Solution, Inc. - www.issi.com

9

Rev. A

04/08/2011

IS42VM81600E / IS42VM16800E / IS42VM32400E

IS45VM81600E / IS45VM16800E / IS45VM32400E

Burst Length

ReadandwriteaccessestotheSDRAMareburstoriented,withtheburstlengthbeingprogrammable,asshownin

MODEREGISTERDEFINITION.Theburstlengthdeterminesthemaximumnumberofcolumnlocationsthatcan

beaccessedforagivenREADorWRITEcommand.Burstlengthsof1,2,4or8locationsareavailableforboththe

sequentialandtheinterleavedbursttypes,andafull-pageburstisavailableforthesequentialtype.Thefull-pageburst

isusedinconjunctionwiththeBURSTTERMINATEcommandtogeneratearbitraryburstlengths.Reservedstates

shouldnotbeused,asunknownoperationorincompatibilitywithfutureversionsmayresult.

WhenaREADorWRITEcommandisissued,ablockofcolumnsequaltotheburstlengthiseffectivelyselected.All

accessesforthatbursttakeplacewithinthisblock,meaningthattheburstwillwrapwithintheblockifaboundaryis

reached.TheblockisuniquelyselectedbyA1-A7(x32),A1-A8(x16)orA1-A9(x8)whentheburstlengthissettotwo;

byA2-A7(x32),A2-A8(x16)orA2-A9(x8)whentheburstlengthissettofour;andbyA3-A7(x32),A3-A8(x16)or

A3-A9(x8)whentheburstlengthissettoeight.Theremaining(leastsignificant)addressbit(s)areusedtoselectthe

startinglocationwithintheblock.Full-pageburstswrapwithinthepageiftheboundaryisreached.

MODE REGISTER DEFINITION

Latency Mode

M6 M5 M4

CAS Latency

0

0

0

Reserved

0

0

1

Reserved

0

1

0

2

0

1

1

3

1

0

0

Reserved

1

0

1

Reserved

1

1

0

Reserved

1

1

1

Reserved

To ensure compatibility with future devices,

should program A11, A10 = "0"

Write Burst Mode

M9

Mode

0

Programmed Burst Length

1

Single Location Access

Operating Mode

M8 M7

M6-M0

Mode

0

0

Defined

Standard Operation

— —

—

All Other States Reserved

Burst Type

M3

Type

0

Sequential

1

Interleaved

Burst Length

M2 M1 M0

M3=0

M3=1

0

0

0

1

1

0

0

1

2

2

0

1

0

4

4

0

1

1

8

8

1

0

0

Reserved

Reserved

1

0

1

Reserved

Reserved

1

1

0

Reserved

Reserved

1

1

1

Full Page

Reserved

Reserved

Address Bus (Ax)

Mode Register (Mx)

(1)

BA1 BA0

A11 A10

A9

A8

A7

A6

A5

A4

A3

A2

A1

A0

BA1

BA0

Mode Register Definition

0

0

Program Mode Register

0

1

Reserved

1

0

Program Extended Mode Register

1

1

Reserved