HYB25D256161CE Datasheet, PDF (25/72 Pages) Infineon Technologies AG – 16M x 16 Double Data Rate Graphics DRAM

HYB25D256161CE-[4/5]
256-Mbit Double Data Rate SGRAM
Functional Description
Data from any Read burst may be truncated with a Burst Terminate command, as shown on Figure 10. The Burst
Terminate latency is equal to the read (CAS) latency, i.e. the Burst Terminate command should be issued x cycles
after the Read command, where x equals the number of desired data element pairs.
Data from any Read burst must be completed or truncated before a subsequent Write command can be issued. If
truncation is necessary, the Burst Terminate command must be used, as shown on Figure 11. The example is
shown for t_DQSS(min). The t_DQSS(max) case, not shown here, has a longer bus idle time. t_DQSS(min) and t_DQSS(max) are
defined in Chapter 3.5.3.
A Read burst may be followed by, or truncated with, a Precharge command to the same bank (provided that Auto
Precharge was not activated). The Precharge command should be issued x cycles after the Read command,
where x equals the number of desired data element pairs (pairs are required by the 2n prefetch architecture). This
is shown on Figure 12 for Read latencies of 2 and 2.5. Following the Precharge command, a subsequent
command to the same bank cannot be issued until t_RP is met. Note that part of the row precharge time is hidden
during the access of the last data elements.
In the case of a Read being executed to completion, a Precharge command issued at the optimum time (as
described above) provides the same operation that would result from the same Read burst with Auto Precharge
enabled. The disadvantage of the Precharge command is that it requires that the command and address busses
be available at the appropriate time to issue the command. The advantage of the Precharge command is that it
can be used to truncate bursts.
CAS Latency = 3
CK
CK
Command
Address
DQS
DQ
Read
BAa, COL n
NOP
BST
CL=3
NOP
NOP
DOa-n
NOP
No further output data after this point.
DQS tristated.
DO a-n = data out from bank a, column n.
Cases shown are bursts of 8 terminated after 4 data elements.
3 subsequent elements of data out appear in the programmed order following DO a-n.
Shown with nominal t_AC, t_DQSCK, and t_DQSQ.
Don’t Care
Figure 10 Terminating a Read Burst (Burst Length = 8)
Datasheet
25
Rev.1.0, 2004-02