K4X56163PE Datasheet, PDF (14/48 Pages) Samsung semiconductor – 16M x16 Mobile DDR SDRAM

K4X56163PE-L(F)G
Mobile-DDR SDRAM
Read Interrupted by a Read
A Burst Read can be interrupted before completion of the burst by new Read command of any bank. When the previous burst is
interrupted, the remaining addresses are overridden by the new address with the full burst length. The data from the first Read com-
mand continues to appear on the outputs until the CAS latency from the interrupting Read command is satisfied. At this point the data
from the interrupting Read command appears. Read to Read interval is minimum 1 Clock.
< Burst Length=4, CAS Latency=3 >
0
1
2
3
4
5
6
CK, CK
Command READ A
DQS
CAS Latency=3
DQs
READ B
NOP
NOP
NOP
NOP
NOP
tSAC
tRPRE
Preamble
Dout A0 Dout A1 Dout B0 Dout B1 Dout B2 Dout B3
7
NOP
8
NOP
Figure.7 Read interrupted by a read timing
Read Interrupted by a Write & Burst Stop
To interrupt a burst read with a write command, Burst Stop command must be asserted to avoid data contention on the I/O bus by
placing the DQs(Output drivers) in a high impedance state. To insure the DQs are tri-stated one cycle before the beginning of the
write operation, Burst stop command must be applied at least 2 clock cycles for CL=2 and at least 3 clock cycles for CL=3 before the
Write command.
< Burst Length=4, CAS Latency=3 >
0
1
2
3
4
5
6
7
8
CK, CK
Command
READ
DQS
CAS Latency=3
DQs
Burst Stop
NOP
tSAC
tRPRE
NOP
NOP
Preamble
Dout 0 Dout 1
WRITE
NOP
tDQSS
tWPRES ^tWPREH
NOP
Din 0 Din 1 Din 2 Din 3
Figure.8 Read interrupted by a write and burst stop timing.
The following functionality establishes how a Write command may interrupt a Read burst.
1. For Write commands interrupting a Read burst, a Burst Terminate command is required to stop the read burst and tristate the
DQ bus prior to valid input write data. Once the Burst Terminate command has been issued, the minimum delay to a Write command
= RU(CL) [CL is the CAS Latency and RU means round up to the nearest integer].
2. It is illegal for a Write command to interrupt a Read with autoprecharge command.
14
March 2004