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Libraries Guide
Chapter 7: Design Elements (LD to NOR16)

LUT1_D, LUT2_D, LUT3_D, LUT4_D

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

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Spartan2
Virtex
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Primitive
Primitive

LUT1_D, LUT2_D, LUT3_D, and LUT4_D are, respectively, 1-, 2-, 3-, and 4-bit look-up-tables (LUTs) with two functionally identical outputs, O and LO. The O output is a general interconnect. The LO output is used to connect to another output within the same CLB slice and to the fast connect buffer.

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

See also “LUT1, 2, 3, 4” and “LUT1_L, LUT2_L, LUT3_L, LUT4_L.”

Table 7_2 LUT3_D Function Table

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