HYB25D256400BT Datasheet, PDF (26/77 Pages) Infineon Technologies AG – 256-Mbit Double Data Rate SDRAM, Die Rev. B

HYB25D256[400/800/160]B[T/C](L)
256-Mbit Double Data Rate SDRAM, Die Rev. B
Data from any Read burst may be truncated with a Burst Terminate command, as shown on Terminating a
Read Burst: CAS Latencies (Burst Length = 8) on page 27. 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 Read to Write:
CAS Latencies (Burst Length = 4 or 8) on page 28. 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 the section on
Writes.
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 com-
mand, where x equals the number of desired data element pairs (pairs are required by the 2n prefetch archi-
tecture). This is shown on Read to Precharge: CAS Latencies (Burst Length = 4 or 8) on page 29 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 Pre-
charge 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.
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2003-01-09, V1.1