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IOBUF_selectIO

Bi-Directional Buffer with Selectable I/0 Interface

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Virtex
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Primitive

figures/x8406.gif

IOBUF and its variants (listed below) are bi-directional buffers whose I/O interface corresponds to a specific I/O standard.The name extensions (LVCMOS2, PCI33_3, PCI33_5, etc.) specify the standard. The S, F, and 2, 4, 6, 8, 12, 16, 24 extensions specify the slew rate (SLOW or FAST) and the drive power (2, 4, 6, 8, 12, 16, 24 mA) for the LVTTL standard variants. For example, IOBUF_F_2 is a bi-directional buffer that uses the LVTTL I/O-signaling standard with a FAST slew and 2mA of drive power.

IOBUF (LVTTL) has selectable drive and slew rates using the DRIVE and FAST or SLOW constraints. The defaults are DRIVE=12 mA and SLOW slew.

IOBUFs are composites of IBUF and OBUFT elements. The O output is X (unknown) when IO (input/output) is Z. IOBUFs can be implemented as interconnections of their component elements.

The hardware implementation of the I/O standards requires that you follow a set of usage rules for the SelectI/O buffer components. Refer to the “SelectI/O Usage Rules” section under the IBUF_selectIO section for information on using these components.

Component
I/O Standard
VCCO
VREF
IOBUF
LVTTL
3.3
N/A
IOBUF_S_2
LVTTL
3.3
N/A
IOBUF_S_4
LVTTL
3.3
N/A
IOBUF_S_6
LVTTL
3.3
N/A
IOBUF_S_8
LVTTL
3.3
N/A
IOBUF_S_12
LVTTL
3.3
N/A
IOBUF_S_16
LVTTL
3.3
N/A
IOBUF_S_24
LVTTL
3.3
N/A
IOBUF_F_2
LVTTL
3.3
N/A
IOBUF_F_4
LVTTL
3.3
N/A
IOBUF_F_6
LVTTL
3.3
N/A
IOBUF_F_8
LVTTL
3.3
N/A
IOBUF_F_12
LVTTL
3.3
N/A
IOBUF_F_16
LVTTL
3.3
N/A
IOBUF_F_24
LVTTL
3.3
N/A
IOBUF_LVCMOS2
LVCMOS2
2.5
N/A
IOBUF_PCI33_3
PCI33_3
3.3
N/A
IOBUF_PCI33_5
PCI33_5
3.3
N/A
IOBUF_PCI66_3
PCI66_3
3.3
N/A
IOBUF_GTL
GTL
N/A
0.80
IOBUF_GTLP
GTL+
N/A
1.00
IOBUF_HSTL_I
HSTL_I
1.5
0.75
IOBUF_HSTL_III
HSTL_III
1.5
0.90
IOBUF_HSTL_IV
HSTL_IV
1.5
0.75
IOBUF_SSTL2_I
SSTL2_I
2.5
1.10
IOBUF_SSTL2_II
SSTL2_II
2.5
1.10
IOBUF_SSTL3_I
SSTL3_I
3.3
0.90
IOBUF_SSTL3_II
SSTL3_II
3.3
1.50
IOBUF_CTT
CTT
3.3
1.50
IOBUF_AGP
AGP
3.3
1.32

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