Datasheet

Figure 14 — Read Burst Showing CAS Latency
7.5.1 Read to Read
Data from a read burst may be concatenated or truncated by a subsequent READ command. The first data from the new burst
follows either the last element of a completed burst or the last desired element of a longer burst that is being truncated. The new
READ command should be issued X cycles after the first READ command, where X equals the number of desired data-out
element pairs (pairs are required by the 2n prefetch architecture). This is shown in Figure 15.
A READ command can be in
itiated on any clock cycle following a previous READ command. Non-consecutive Reads are shown
in Figure 16.
Full-speed random read accesses within a page or pages can be performed as shown in Figure 17.
7.5.2 Read Burst Terminate
Data from any READ burst may be truncated with a BURST TERMINATE command, as shown in Figure 18. TheBURST
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 desired data-out element pairs.
7.5.3 Read to Write
Data from 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 in Figure 19 for the case of nominal tDQSS .
5.5.4 Read to Precharge
A Read burst may be followed by or truncated with a PRECHARGE command to the same bank (provided Auto Precharge was
not activated). The PRECHARGE command should be issued X cycles after the READ command, where X equal the number of
desired data-out element pairs. This is shown in Figure 20. Following the PRECHARGE command, a subsequent command to
the same bank cannot be issued until tRP is met. Note that part of the row precharge time is hidden during the access of the last
data-out 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 Read burst with Auto Precharge enabled. The disadvantage of the
PRECHARGE command is that it requires that the command and address buses 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.
AS4C16M16MD1
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