ESMT

M13L32321A (2G)

Elite Semiconductor Memory Technology Inc.

Publication Date : Oct. 2012

Revision : 1.0

18/48

Read

This command is used after the row activate command to initiate the burst read of data. The read command is initiated by activating

CS , RAS , CAS , and deasserting WE at the same clock rising edge as described in the command truth table. The length of the

burst and the CAS latency time will be determined by the values programmed during the MRS command.

Write

This command is used after the row activate command to initiate the burst write of data. The write command is initiated by activating

CS , RAS , CAS , and WE at the same clock rising edge as describe in the command truth table. The length of the burst will be

determined by the values programmed during the MRS command.

Burst Read Operation

Burst Read operation in DDR SDRAM is in the same manner as the current SDRAM such that the Burst read command is issued by

activation. The address inputs determine the starting address for the Burst. The Mode Register sets type of burst (Sequential or

interleave) and burst length (2, 4, 8). The first output data is available after the CAS Latency from the READ command, and the

consecutive data are presented on the falling and rising edge of Data Strobe (DQS) adopted by DDR SDRAM until the burst length

is completed.

<Burst Length = 4, CAS Latency = 3>

Burst Write Operation

The Burst Write command is issued by having CS , CAS and WE low while holding RAS high at the rising edge of the clock

(CLK). The address inputs determine the starting column address. There is no write latency relative to DQS required for burst write

rising edge of the clock (CLK) that the write command is issued. The remaining data inputs must be supplied on each subsequent

falling and rising edge of Data Strobe until the burst length is completed. When the burst has been finished, any additional data

supplied to the DQ pins will be ignored.

<Burst Length = 4>

Note * 1: The specific requirement is that DQS be valid (High or Low) on or before this CLK edge. The case shown (DQS going from

High-Z to logic Low) applies when no writes were previously in progress on the bus. If a previous write was in progress, DQS

0

1

23

4

5

67

8

COM M A N D

R EAD A

NOP

NO P

NO P

NO P

NOP

NO P

NO P

NO P

CL K

CL K

CA S L a t e n c y = 3

DQS

DQ ' s

01

23

4

5

6

7

8

C O MMA N D

NOP

WR IT E A

NO P

NOP

NO P

NO P

NO P

NO P

CL K

CL K

DQS

DQ' s

WR IT E B

*1

*1