Specifications

Figure 1-9: ALM in Shared Arithmetic Mode for Cyclone V Devices
datae0
carry_in
shared_arith_in
shared_arith_out
carry_out
dataa
datab
datac
datad
datae1
4-Input
LUT
4-Input
LUT
4-Input
LUT
4-Input
LUT
labclk
reg0
To General or
Local Routing
reg1
reg2
reg3
Shared Arithmetic Chain
The shared arithmetic chain available in enhanced arithmetic mode allows the ALM to implement a 3-input
adder. This significantly reduces the resources necessary to implement large adder trees or correlator
functions.
The shared arithmetic chain can begin in either the first or sixth ALM in a LAB.
Similar to carry chains, the top and bottom half of the shared arithmetic chains in alternate LAB columns
can be bypassed. This capability allows the shared arithmetic chain to cascade through half of the ALMs in
an LAB while leaving the other half available for narrower fan-in functionality. In every LAB, the column
is top-half bypassable; while in MLAB, columns are bottom-half bypassable.
The Quartus II Compiler creates shared arithmetic chains longer than 20 ALMs (10 ALMs in arithmetic or
shared arithmetic mode) by linking LABs together automatically. To enhance fitting, a long shared arithmetic
chain runs vertically, allowing fast horizontal connections to the TriMatrix memory and DSP blocks. A
shared arithmetic chain can continue as far as a full column.
Document Revision History
ChangesVersionDate
• Added link to the known document issues in the Knowledge Base.
• Removed register chain outputs information in ALM output section.
•
Removed reg_chain_in and reg_chain_out ports in ALM high-
level block diagram and ALM connection details diagram.
2013.05.06May 2013
Logic Array Blocks and Adaptive Logic Modules in Cyclone V Devices
Altera Corporation
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Document Revision History
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2013.05.06