5. Design Partition Guidelines

5.　　Design Partition Guidelines

　　　　types of optimizations are prevented by partition boundaries, you can structure or modify your partitions to avoid these limitations.

5.1　 Register Partition Inputs and Outputs

　　　　Registers minimize the delays on inter-partition paths and prevent the need for cross-boundary optimizations

　　　　floorplan

　　　　If a design cannot include both input and output registers for each partition due to latency or resource utilization concerns, Registered outputs

5.2　 Minimize Cross-Partition-Boundary I/O

　　　　makes partitions more independent for both logic and placement optimization.

　　　　most important for timing-critical and high-speed connections between partitions, especially in cases where the input and output of each partition is not registered.

　　　　Figure 16–3. Minimizing I/O Between Partitions by Moving the Partition Boundary

　　　　Figure 16–4. Minimizing I/O between Partitions by Modifying Glue Logic

5.3　 Examine the Need for Logic Optimization Across Partitions 

The following guidelines ensure that your design does not require logic optimization across partition boundaries:

5.3.1　　Keep Logic in the Same Partition for Optimization and Merging

the logic requires logic optimization or merging, need be in the same partition

optimization: If a combinational logic path is split across two partitions, the logic cannot be optimized or merged into one logic cell in the device.

merging:  In a flat design, the Fitter can also merge logical instantiations into the same physical device resource. 

5.3.1.1 Merging PLLs and Transceivers (GXB) :  no restrictions for PLLs and high-speed transceiver blocks when setting up partitions.

5.3.2　　Keep Constants in the Same Partition as Logic

Figure 16–6. Keeping Constants in the Same Partition as the Logic They Feed 

Within the single merged partition, the Quartus II software can use the constants to optimize and remove much of the logic in block B (shown in gray), as shown in Figure 16–6. 

5.3.3　　Avoid Signals That Drive Multiple Partition I/O or Connect I/O Together 

If one signal from a higher-level partition feeds two input ports of the same partition, feed the one signal into the partition, and then make the two connections within the partition. 

If an output port drives an input port of the same partition, 

If an input port drives an output port directly, 

5.3.4　　Invert Clocks in Destination Partitions” on page 16–17
5.3.5　　Connect I/O Pin Directly to I/O Register for Packing Across Partition Boundaries” on page 16–17
5.3.6　　Do Not Use Internal Tri-States” on page 16–21
5.3.7　　Include All Tri-State and Enable Logic in the Same Partition” on page 16–22
5.3.8　　Include Bidirectional I/O Registers in the Same Partition (For Older Device Families)” on page 16–23
5.3.9　　Summary of Guidelines Related to Logic Optimization Across Partitions

5.4　 Consider a Cascaded Reset Structure