K4S280432B

CMOS SDRAM

Rev. 0.0 Aug. 1999

SIMPLIFIED TRUTH TABLE

(V=Valid, X=Don

′t care, H=Logic high, L=Logic low)

Command

CKEn-1

CKEn

CS

RAS

CAS

WE

DQM

Note

Register

Mode register set

H

X

L

L

L

L

X

OP code

1,2

Refresh

Auto refresh

H

H

L

L

L

H

X

X

3

Self

refresh

Entry

L

3

Exit

L

H

L

H

H

H

X

X

3

H

X

X

X

3

Bank active & row addr.

H

X

L

L

H

H

X

V

Row address

Read &

column address

Auto precharge disable

H

X

L

H

L

H

X

V

L

Column

address

4

Auto precharge enable

H

4,5

Write &

column address

Auto precharge disable

H

X

L

H

L

L

X

V

L

Column

address

4

Auto precharge enable

H

4,5

Burst stop

H

X

L

H

H

L

X

X

6

Precharge

Bank selection

H

X

L

L

H

L

X

V

L

X

All banks

X

H

Clock suspend or

active power down

Entry

H

L

H

X

X

X

X

X

L

V

V

V

Exit

L

H

X

X

X

X

X

Precharge power down mode

Entry

H

L

H

X

X

X

X

X

L

H

H

H

Exit

L

H

H

X

X

X

X

L

V

V

V

DQM

H

V

X

7

No operation command

H

X

H

X

X

X

X

X

L

H

H

H

1. OP Code : Operand code

2. MRS can be issued only at all banks precharge state.

A new command can be issued after 2 CLK cycles of MRS.

3. Auto refresh functions are as same as CBR refresh of DRAM.

The automatical precharge without row precharge command is meant by "Auto".

Auto/self refresh can be issued only at all banks precharge state.

5. During burst read or write with auto precharge, new read/write command can not be issued.

Another bank read/write command can be issued after the end of burst.

6. Burst stop command is valid at every burst length.

7. DQM sampled at positive going edge of a CLK and masks the data-in at the very CLK (Write DQM latency is 0),

but makes Hi-Z state the data-out of 2 CLK cycles after. (Read DQM latency is 2)

Notes :

X