EP3SE50F780I3N Altera, EP3SE50F780I3N Datasheet - Page 45

• Manufacturer Part Number: EP3SE50F780I3N
• Description: Stratix III
• Manufacturer: Altera

Figure 2–8. 4
Altera Corporation
October 2007
sel0[1..0]
sel1[1..0]
inputa
inputb
inputc
inputd
×
2 Crossbar Switch Example
4 × 2 Crossbar Switch
In the case of implementing 2 six-input functions in one ALM, four inputs
must be shared and the combinational function must be the same. For
example, a 4
inputs and unique select lines) can be implemented in one ALM, as
shown in
datad, while the unique select lines are datae0 and dataf0 for
function0, and datae1 and dataf1 for function1. This crossbar
switch consumes four LUTs in a four-input LUT-based architecture.
In a sparsely used device, functions that could be placed into one ALM
may be implemented in separate ALMs by the Quartus II software in
order to achieve the best possible performance. As a device begins to fill
up, the Quartus II software automatically utilizes the full potential of the
Stratix III ALM. The Quartus II Compiler automatically searches for
functions of common inputs or completely independent functions to be
placed into one ALM and to make efficient use of the device resources. In
addition, you can manually control resource usage by setting location
assignments.
Any six-input function can be implemented utilizing inputs dataa,
datab, datac, datad, and either datae0 and dataf0 or datae1 and
dataf1. If datae0 and dataf0 are utilized, the output is driven to
register0, and/or register0 is bypassed and the data drives out to
the interconnect using the top set of output drivers (refer to
If datae1 and dataf1 are utilized, the output drives to register1
and/or bypasses register1 and drives to the interconnect using the
bottom set of output drivers. The Quartus II Compiler automatically
selects the inputs to the LUT. ALMs in normal mode support register
packing.
Logic Array Blocks and Adaptive Logic Modules in Stratix III Devices
out0
out1
Figure
×
2 crossbar switch (two 4-to-1 multiplexers with common
2–8. The shared inputs are dataa, datab, datac, and
datae0
datae1
dataf0
dataf1
dataa
datab
datac
datad
Implementation in 1 ALM
Stratix III Device Handbook, Volume 1
(Function0)
(Function1)
Six-Input
Six-Input
LUT
LUT
combout0
combout1
Figure
2–9).
2–11