Adaptive Logic Modules
Figure 2–10. Template for Supported Seven-Input Functions in Extended LUT Mode
datae0
datac
dataa
5-Input
LUT
datab
To general or
local routing
datad
dataf0
combout0
To general or
local routing
D
Q
5-Input
LUT
reg0
datae1
dataf1
(1)
This input is available
for register packing.
Note to Figure 2–10:
(1) If the seven-input function is unregistered, the unused eighth input is available for register packing. The second
register, reg1, is not available.
Arithmetic Mode
The arithmetic mode is ideal for implementing adders, counters,
accumulators, wide parity functions, and comparators. An ALM in
arithmetic mode uses two sets of two four-input LUTs along with two
dedicated full adders. The dedicated adders allow the LUTs to be
available to perform pre-adder logic; therefore, each adder can add the
output of two four-input functions. The four LUTs share the dataaand
databinputs. As shown in Figure 2–11, the carry-in signal feeds to
adder0, and the carry-out from adder0feeds to carry-in of adder1. The
carry-out from adder1drives to adder0of the next ALM in the LAB.
ALMs in arithmetic mode can drive out registered and/or unregistered
versions of the adder outputs.
2–14
Altera Corporation
May 2007
Stratix II Device Handbook, Volume 1
ALTERA [ ALTERA CORPORATION ]
