| XC3000 | XC4000E | XC4000X | XC5200 | XC9000 | Spartan | SpartanXL | Virtex |
|---|---|---|---|---|---|---|---|
| Primitive | Primitive | Primitive | Primitive | Primitive | Primitive | Primitive | Primitive |
BUF is a general purpose, non-inverting buffer.
In FPGA architectures, BUF is usually not necessary and is removed by the partitioning software (MAP). The BUF element can be preserved for reducing the delay on a high fan-out net, for example, by splitting the net and reducing capacitive loading. In this case, the buffer is preserved by attaching an X (explicit) attribute to both the input and output nets of the BUF.
In CPLD architecture, BUF is usually removed, unless you inhibit optimization by applying the OPT=OFF attribute to the BUF symbol or by using the LOGIC_OPT=OFF global attribute.
