Altera QDRII SRAM Controller MegaCore Function Bedienungsanleitung PDF herunterladen (Seite 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 03040304

0002

01 02 03 0404

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Altera QDRII SRAM Controller MegaCore Function Bedienungsanleitung Seite 50