K4H280438B-TCA0 Datasheet, PDF (20/53 Pages) Samsung semiconductor – 128Mb DDR SDRAM

128Mb DDR SDRAM
3.3 Essential Functionality for DDR SDRAM
The essential functionality that is required for the DDR SDRAM device is described in this chapter
3.3.1 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 asserting CS and CAS low while holding RAS and WE high at the rising edge of the
clock(CK) after tRCD from the bank activation. The address inputs (A0~A9) 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 pre-
sented 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= 2, 2.5 >
0
CK
CK
Command READ A
1
NOP
2
NOP
3
NOP
4
NOP
5
NOP
6
NOP
7
NOP
8
NOP
CAS Latency=2
DQS
DQ ′s
t_RPRE
t_RPST
Dout 0 Dout 1 Dout 2 Dout 3
CAS Latency=2.5
DQS
DQ ′s
Dout 0 Dout 1 Dout 2 Dout 3
Figure 9. Burst read operation timing
- 20 -
REV. 1.0 November. 2. 2000