Rev0.2, Jan. 2007

CMS3216LAx-75xx

Register Definition

There are two mode registers which contain settings to

achieve low power consumption. The two registers : Mode

Register and Extended Mode Register are discussed below.

Mode Register

The mode register is used to define the specific mode of

operation of the SDRAM. This definition includes the selec-

tion of a burst length, a burst type, a CAS latency, an operat-

ing mode and a write burst mode, as shown in Table 1. The

mode register is programmed via the LOAD MODE REGIS-

TER command and will retain the stored information until it is

programmed again or the device loses power. Mode Register

bits M0-M2 specify the burst length, M3 specifies the type of

burst (sequential or interleaved), M4-M6 specify the CAS

latency, M7 and M8 specify the operating mode, M9 specifies

the write burst mode, M10 and M11 should be set to zero.The

Mode register must be loaded when all banks are idle, and the

controller must wait the specified time before initiating the

subsequent operation. Violating either of these requirements

will result in unspecified operation.

Burst Length

Read and write accesses to the SDRAM are burst oriented. The

burst length is programmable, as shown in Table 2. The burst

length determines the maximum number of column locations

that can be accessed for a given READ or WRITE command.

Burst lengths of 1,2, 4, or 8 locations are available for both the

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Note :

1. The two AUTO REFRESH commands at T4 and T9 may be applied before either LOAD MODE REGISTER (LMR) command.

2. PRE = PRECHARGE command, LMR = LOAD MODE REGISTER command, AR = AUTO REFRESH command, ACT = ACTIVE command, RA = Row Address, BA = Bank

Address

3. The Load Mode Register for both MR/EMR and 2 Auto Refresh commands can be in any order; However, all must occur prior to an Active command.

Key

Key

Key

RAa

HiZ

HiZ

CLK

CKE

/CS

/RAS

/CAS

ADDR

BS

A10/AP

DQ

/WE

DQM

High level is necessary

Precharge

(All Bank)

Auto

Refresh

Auto

Refresh

Normal

MRS

Extended

MRS

Row Active

a Bank

BS