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3.2.4.5.3. QDR4 Interface
The external QDR4 SRAM is well suited for fast table look ups and external statistics counter storage due to the fast random access capabilities of QDR4 SRAM. QDR4 SRAM transfers 4 data words per clock cycle. QDR4 SRAM also has two independent bidirectional double data rate ports that support concurrent read/write transactions on both ports.
The multiple access ports of the QDR4 SRAM results in the internal interface providing 8 – Avalon® memory-mapped interface interfaces for this external memory device. The interface is shown below:
ccip_std_afu Direction | Width | Signal Name | Description |
---|---|---|---|
input |
|
qdr_avmm_clk |
266 MHz clock sourced from EMIF |
input |
|
qdr_avmm_reset_n |
Active low reset to user logic. Reset for the user clock domain. Asynchronous assertion and synchronous de-assertion |
input |
|
qdr_avmm_waitrequest [7:0] |
Wait-request is asserted when controller Avalon® memory-mapped interface interface is busy |
input |
[35:0] |
qdr_avmm_readdata [7:0] |
Read data from external memory |
input |
|
qdr_avmm_readdatavalid [7:0] |
Indicates readdata is valid when high |
output |
[2:0] |
qdr_avmm_burstcount [7:0] |
Number of transfers in each read/write burst |
output |
[35:0] |
qdr_avmm_writedata [7:0] |
AFU supplied data to written to external memory |
output |
[21:0] |
qdr_avmm_address [7:0] |
Word address for Avalon® memory-mapped interface interface of memory controller |
output |
|
qdr_avmm_write [7:0] |
Write request from AFU |
output |
|
qdr_avmm_read [7:0] |
Read request from AFU |