EPF6016 datasheet(13/52 Pages) ALTERA

13 / 52 page

Altera Corporation

FLEX 6000 Programmable Logic Device Family Data Sheet

Figure 6. Cascade Chain Operation

LE Operating Modes

The FLEX 6000 LE can operate in one of the following three modes:

■

Normal mode

■

Arithmetic mode

■

Counter mode

Each of these modes uses LE resources differently. In each mode, seven

available inputs to the LE—the four data inputs from the LAB local

interconnect, the feedback from the programmable register, and the

carry-in and cascade-in from the previous LE—are directed to different

destinations to implement the desired logic function. LAB-wide signals

provide clock, asynchronous clear, synchronous clear, and synchronous

load control for the register. The Altera software, in conjunction with

parameterized functions such as LPM and DesignWare functions,

automatically chooses the appropriate mode for common functions such

as counters, adders, and multipliers. If required, the designer can also

create special-purpose functions to use an LE operating mode for optimal

performance.

Figure 7 shows the LE operating modes.

d[3..0]

LE 2

LUT

d[7..4]

LE 3

LUT

n + 1

LUT

d[3..0]

LUT

d[7..4]

LUT

LE 2

LE 3

AND Cascade Chain

OR Cascade Chain

d[(4

n-1)..4(n-1)]

d[(4

n-1)..4(n-1)]

EPF6016 Datasheet(PDF) 13 Page - Altera Corporation

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