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White Electronic Designs Corporation • (602) 437-1520 • www.whiteedc.com

White Electronic Designs

WEDPNF8M721V-XBX

vents unwanted commands from being registered during

idle or wait states. Operations already in progress are not

affected.

LOAD MODE REGISTER

The Mode Register is loaded via inputs A0-11. See Mode

Register heading in the Register Definition section. The LOAD

MODE REGISTER command can only be issued when all

banks are idle, and a subsequent executable command

cannot be issued until tMRD is met.

ACTIVE

The ACTIVE command is used to open (or activate) a row in

a particular bank for a subsequent access. The value on the

BA0, BA1 inputs selects the bank, and the address pro-

vided on inputs A0-11 selects the row. This row remains

active (or open) for accesses until a PRECHARGE command

is issued to that bank. A PRECHARGE command must be

issued before opening a different row in the same bank.

READ

The READ command is used to initiate a burst read access

to an active row. The value on the BA0, BA1 inputs selects

the bank, and the address provided on inputs A0-8 selects

the starting column location. The value on input A10 deter-

NAME (FUNCTION)

NAME (FUNCTION)

NAME (FUNCTION)

NAME (FUNCTION)

NAME (FUNCTION)

CS

CS

CS

CS

CS

RAS

RAS

RAS

RAS

RAS

CAS

CAS

CAS

CAS

CAS

WE

WE

WE

WE

WE

DQM

DQM

DQM

DQM

DQM

ADDR

ADDR

ADDR

ADDR

ADDR

I/Os

I/Os

I/Os

I/Os

I/Os

COMMAND INHIBIT (NOP)

H

X

X

X

X

X

X

NO OPERATION (NOP)

L

H

H

H

X

X

X

ACTIVE (Select bank and activate row) ( 3)

L

L

H

H

X

Bank/Row

X

READ (Select bank and column, and start READ burst) (4)

L

H

L

H

Bank/Col

X

WRITE (Select bank and column, and start WRITE burst) (4)

L

H

L

L

Bank/Col

Valid

BURST TERMINATE

L

H

H

L

X

X

Active

PRECHARGE (Deactivate row in bank or banks) ( 5)

L

L

H

L

X

Code

X

AUTO REFRESH or SELF REFRESH (Enter self refresh mode) (6, 7)

L

L

L

H

X

X

X

LOAD MODE REGISTER (2)

L

L

L

L

X

Op-Code

X

Write Enable/Output Enable (8)

–

–

–

–

L

–

Active

Write Inhibit/Output High-Z (8)

–

–

–

–

H

–

High-Z

mines whether or not AUTO PRECHARGE is used. If AUTO

PRECHARGE is selected, the row being accessed will be

precharged at the end of the READ burst; if AUTO

PRECHARGE is not selected, the row will remain open for

subsequent accesses. Read data appears on the I/Os sub-

ject to the logic level on the DQM inputs two clocks earlier.

If a given DQM signal was registered HIGH, the correspond-

ing I/Os will be High-Z two clocks later; if the DQM signal

was registered LOW, the I/Os will provide valid data.

WRITE

The WRITE command is used to initiate a burst write access

to an active row. The value on the BA0, BA1 inputs selects

the bank, and the address provided on inputs A0-8 se-

lects the starting column location. The value on input A10

determines whether or not AUTO PRECHARGE is used. If

AUTO PRECHARGE is selected, the row being accessed will

be precharged at the end of the WRITE burst; if AUTO

PRECHARGE is not selected, the row will remain open for

subsequent accesses. Input data appearing on the I/Os is

written to the memory array subject to the DQM input logic

level appearing coincident with the data. If a given DQM

signal is registered LOW, the corresponding data will be

written to memory; if the DQM signal is registered HIGH,

the corresponding data inputs will be ignored, and a WRITE

will not be executed to that byte/column location.

NOTES:

1. CKE is HIGH for all commands shown except SELF REFRESH.

2. A0-11 define the op-code written to the Mode Register.

3. A0-11 provide row address, and BA0, BA1 determine which bank is made active.

4. A0-8 provide column address; A10 HIGH enables the auto precharge feature (nonpersistent), while A10 LOW disables the auto precharge feature; BA0, BA1

determine which bank is being read from or written to.

5. A10 LOW: BA0, BA1 determine the bank being precharged. A10 HIGH: All banks precharged and BA0, BA1 are “Don’t Care.”

6. This command is AUTO REFRESH if CKE is HIGH; SELF REFRESH if CKE is LOW.

7. Internal refresh counter controls row addressing; all inputs and I/Os are “Don’t Care” except for CKE.

8. Activates or deactivates the I/Os during WRITEs (zero-clock delay) and READs (two-clock delay).