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DPCLK0 参数 Datasheet PDF下载

DPCLK0图片预览
型号: DPCLK0
PDF下载: 下载PDF文件 查看货源
内容描述: 的Cyclone III器件手册 [Cyclone III Device Handbook]
分类和应用:
文件页数/大小: 274 页 / 7302 K
品牌: ALTERA [ ALTERA CORPORATION ]
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Chapter 3: Memory Blocks in the Cyclone III Device Family  
3–17  
Design Considerations  
In this mode, you also have two output choices: Old Data mode or Don't Care mode.  
In Old Data mode, a read-during-write operation to different ports causes the RAM  
outputs to reflect the old data at that address location. In Don't Care mode, the same  
operation results in a “Don't Care” or unknown value on the RAM outputs.  
f
For more information about how to implement the desired behavior, refer to the  
Internal Memory (RAM and ROM) User Guide.  
Figure 3–17 shows a sample functional waveform of mixed port read-during-write  
behavior for the Old Data mode. In Don't Care mode, the old data is replaced with  
“Don't Care”.  
Figure 3–17. Mixed Port Read-During-Write: Old Data Mode  
clk_a&b  
wren_a  
address_a  
a
b
A
B
C
D
E
F
data_a  
rden_b  
address_b  
a
b
B
a (old data)  
D
E
b (old data)  
A
q_b (asynch)  
1
For mixed-port read-during-write operation with dual clocks, the relationship  
between the clocks determines the output behavior of the memory. If you use the  
same clock for the two clocks, the output is the old data from the address location.  
However, if you use different clocks, the output is unknown during the mixed-port  
read-during-write operation. This unknown value may be the old or new data at the  
address location, depending on whether the read happens before or after the write.  
Conflict Resolution  
When you are using M9K memory blocks in true dual-port mode, it is possible to  
attempt two write operations to the same memory location (address). Because there is  
no conflict resolution circuitry built into M9K memory blocks, this results in unknown  
data being written to that location. Therefore, you must implement conflict-resolution  
logic external to the M9K memory block.  
December 2011 Altera Corporation  
Cyclone III Device Handbook  
Volume 1  
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