Logic Elements
Figure 2–9. Carry Select Chain
LAB Carry-In
0
1
LAB Carry-In
Carry-In0
Sum1
Sum2
Sum3
Sum4
Sum5
A1
B1
LE0
LE1
LE2
LE3
LE4
Carry-In1
A2
B2
LUT
LUT
data1
data2
Sum
A3
B3
A4
B4
LUT
LUT
A5
B5
0
1
Carry-Out0
Carry-Out1
Sum6
Sum7
Sum8
Sum9
Sum10
A6
B6
LE5
LE6
LE7
LE8
LE9
A7
B7
A8
B8
A9
B9
A10
B10
To top of adjacent LAB
LAB Carry-Out
The Quartus II software automatically creates carry chain logic during
design processing, or the designer can create it manually during design
entry. Parameterized functions such as LPM functions automatically take
advantage of carry chains for the appropriate functions. The Quartus II
software creates carry chains longer than 10 LEs by linking adjacent LABs
within the same row together automatically. A carry chain can extend
horizontally up to one full LAB row, but they do not extend between LAB
rows.
2–14
MAX II Device Handbook, Volume 1
Core Version a.b.c variable
Altera Corporation
August 2006
INTEL [ INTEL ]
