Xilinx 8.2i manual No logic replication, Output File Name

R

MAP Options

The syntax for the Spartan 3/3E/3L, Virtex-4/-FX/-LX/-SX, Virtex-II, Virtex-II Pro/-X architectures follows:

–k {4 5 678}

You can specify the maximum size function that is covered. The default is 4. Covering to 5, 6, 7 or 8 input functions results in the use of F5MUX, F6MUX, and FXMUX.

By mapping input functions into single CLBs, the –k option may produce a mapping with fewer levels of logic, thus eliminating a number of CLB-to-CLB delays. However, using the –k option may prevent logic from being packed into CLBs in a way that minimizes CLB utilization.

For synthesis-based designs, specifying –k 4 has no effect. This is because MAP combines smaller input functions into large functions such as F5MUX, F6MUX, F7MUX and F8MUX.

–l (No logic replication)

By default (without the –l option), MAP performs logic replication. Logic replication is an optimization method in which MAP operates on a single driver that is driving multiple loads and maps it as multiple components, each driving a single load (refer to the following figure). Logic replication results in a mapping that often makes it easier to meet your timing requirements, since some delays can be eliminated on critical nets. To turn off logic replication, you must specify the -l option.

Without Logic Replication

With Logic Replication

C D

A

B

Function

Generator

Function

Generator

C D

A	Function
	Generator
B

Replicated

E F

	E
Function	F
	Function
Generator	Generator

X6973

Figure 7-2:Logic Replication (–l Option)

–o (Output File Name)

–o outfile[.ncd]

Specifies the name of the output NCD file for the design. The .ncd extension is optional. The output file name and its location are determined in the following ways:

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