Previous

LUT1, 2, 3, 4

1-, 2-, 3-, 4-Bit Look-Up-Table with General Output

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

figures/x8358.gif

figures/x8379.gif

figures/x8382.gif

figures/x8385.gif

LUT1, LUT2, LUT3, and LUT4 are, respectively, 1-, 2-, 3-, and 4-bit look-up-tables (LUTs) with general output (O).

A mandatory INIT attribute, with an appropriate number of hexadecimal digits for the number of inputs, must be attached to the LUT to specify its function.

LUT1 provides a look-up-table version of a buffer or inverter.

LUTs are the basic Virtex building blocks. Two LUTs are available in each CLB slice; four LUTs are available in each CLB. The variants, “LUT1_D, LUT2_D, LUT3_D, LUT4_D” and “LUT1_L, LUT2_L, LUT3_L, LUT4_L”, provide additional types of outputs that can be used by different timing models for more accurate pre-layout timing estimation.

Inputs
Outputs
I2
I1
I0
O
0
0
0
INIT[0]
0
0
1
INIT[1]
0
1
0
INIT[2]
0
1
1
INIT[3]
1
0
0
INIT[4]
1
0
1
INIT[5]
1
1
0
INIT[6]
1
1
1
INIT[7]
INIT = binary equivalent of the hexadecimal number assigned to the INIT attribute

LUT3 Function Table

Next