ACEX1 datasheet(20/86 Pages) ETC

20 / 86 page

Altera Corporation

ACEX 1K Programmable Logic Device Family Data Sheet

LE Operating Modes

The ACEX 1K LE can operate in the following four modes:

Normal mode

Arithmetic mode

Up/down counter mode

Clearable 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. Three inputs to the

LE provide clock, clear, and preset 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 that use a specific

LE operating mode for optimal performance.

The architecture provides a synchronous clock enable to the register in all

four modes. The Altera software can set DATA1 to enable the register

synchronously, providing easy implementation of fully synchronous

designs.

Figure 11 shows the ACEX 1K LE operating modes.

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