Altera QDRII SRAM Controller MegaCore Function - Manual (Page 49)

Altera Corporation MegaCore Version 9.1 3–17
November 2009 QDRII SRAM Controller MegaCore Function User Guide
Functional Description
Figure 3–14 shows the behavior of a single read request for a burst of four
(wide mode). The read occurs on the Avalon interface, the slave issues a
latent read answer. The read command is sent to the memory with the
address.
Figure 3–14. Isolated Read—Burst of Four (Wide Mode)
Burst
Bursts only apply to burst of four, (narrow mode), refer to
Figure 3–15 on
page 3–18 . For the other two modes, there is no such concept as all the
data required on the QDRII SRAM interface is available for a single
Avalon read. The burst consists of two consecutive read requests. The
controller sends one read request to the memory, which returns the four
half cycles of value. After resynchronization, the data is sent back to the
Avalon interface.
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]
0001 0001
01020304 01020304
0001 0001
01 02 03 04 04