ARRIAGX_09 Datasheet, PDF (45/234 Pages) Altera Corporation – The ArriaTM GX family of devices combines 3.125 gigabits per second (Gbps) serial transceivers

Chapter 2: Arria GX Architecture
2–39
Adaptive Logic Modules
Figure 2–35. Conditional Operation Example
X[0]
Y[0]
syncdata
X[1]
Y[1]
Carry Chain
ALM 1
Adder output
is not used.
Comb & _X[0]
Adder
Logic
Comb &
Adder
Logic
syncload
X[1]
ALM 2
syncload
R[0]
DQ
reg0
R[1]
DQ
reg1
To general or
local routing
To general or
local routing
X[2]
Comb &
Adder ^X[2]
Y[2]
Logic
R[2]
DQ
To general or
local routing
syncload
reg0
Comb &
Adder
Logic
carry_out
To local routing &
then to LAB-wide
syncload
Arithmetic mode also offers clock enable, counter enable, synchronous up/down
control, add/subtract control, synchronous clear, and synchronous load. The LAB
local interconnect data inputs generate the clock enable, counter enable, synchronous
up/down and add/subtract control signals. These control signals can be used for the
inputs that are shared between the four LUTs in the ALM. The synchronous clear and
synchronous load options are LAB-wide signals that affect all registers in the LAB.
The Quartus II software automatically places any registers that are not used by the
counter into other LABs.
Carry Chain
Carry chain provides a fast carry function between the dedicated adders in arithmetic
or shared arithmetic mode. Carry chains can begin in either the first ALM or the fifth
ALM in a LAB. The final carry-out signal is routed to an ALM, where it is fed to local,
row, or column interconnects.
The Quartus II Compiler automatically creates carry chain logic during compilation,
or you 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 Compiler creates carry chains longer than 16 (8 ALMs in
arithmetic or shared arithmetic mode) by linking LABs together automatically. For
enhanced fitting, a long carry chain runs vertically allowing fast horizontal
connections to TriMatrix memory and DSP blocks. A carry chain can continue as far as
a full column. To avoid routing congestion in one small area of the device when a high
fan-in arithmetic function is implemented, the LAB can support carry chains that only
use either the top half or bottom half of the LAB before connecting to the next LAB.
© December 2009 Altera Corporation
Arria GX Device Handbook, Volume 1