Altera QDRII SRAM Controller MegaCore Function - Manual (Page 50)

3–18 MegaCore Version 9.1 Altera Corporation
QDRII SRAM Controller MegaCore Function User Guide November 2009
Interfaces & Signals
Figure 3–15. Burst—Burst of Four (Narrow Mode)
Bursts with Pauses
Bursts with pauses only applies to bursts of four, (narrow mode). When
several read requests to non-consecutive addresses occur, it takes more
time to get the data from the memory (it take two cycles per read access)
than time needed to request them.
Figure 3–16 on page 3–19 shows a read
followed by two reads to consecutive addresses. As the first two requests
are not to consecutive addresses, the controller has to pause the read
requests to insert a clock cycle. The following two reads still get
concatenated to make a burst of four, avoiding loss of bandwidth.
avl_clk
avl_read
avl_data_rd[19:0]
avl_wait_request_rd
avl_data_read_valid
avl_data_rd[17:0]
qdrii_k
qdrii_a[19:0]
qdrii_rpsn
qdrii_cq
qdrii_cqn
qdrii_q[17:0]
0002 0003
0102 0304 0304
0002
01 02 03 04 04