| Element | XC3000 | XC4000E | XC4000X | XC5200 | XC9000 | Spartan | SpartanXL | Virtex |
|---|---|---|---|---|---|---|---|---|
| IBUF | Primitive | Primitive | Primitive | Primitive | Primitive | Primitive | Primitive | Primitive |
| IBUF4, IBUF8, IBUF16 | Macro | Macro | Macro | Macro | Macro | Macro | Macro | Macro |
IBUF, IBUF4, IBUF8, and IBUF16 are single- and multiple-input buffers. An IBUF isolates the internal circuit from the signals coming into a chip. IBUFs are contained in input/output blocks (IOBs). IBUF inputs (I) are connected to an IPAD or an IOPAD. IBUF outputs (O) are connected to the internal circuit.
For Virtex, refer to the “IBUF_selectIO” section for information on IBUF variants with selectable I/O interfaces. IBUF, 4, 8, and 16 use the LVTTL standard.
Figure 6.3 IBUF8 Implementation XC3000, XC4000, XC5200, XC9000, Spartans, Virtex |  |
