LFSC datasheet(7/237 Pages) LATTICE

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2-3

Architecture

Lattice Semiconductor

LatticeSC/M Family Data Sheet

PFU Blocks

The core of the LatticeSC devices consists of PFU blocks. The PFUs can be programmed to perform Logic, Arith-

metic, Distributed RAM and Distributed ROM functions.

Each PFU block consists of four interconnected slices, numbered 0-3 as shown in Figure 2-2. All the interconnec-

tions to and from PFU blocks are from routing. There are 53 inputs and 25 outputs associated with each PFU block.

Figure 2-2. PFU Diagram

Slice

Each slice contains two LUT4 lookup tables feeding two registers (programmed to be in FF or Latch mode), and

some associated logic that allows the LUTs to be combined to implement 5, 6, 7 and 8 Input LUTs (LUT5, LUT6,

LUT7 and LUT8). There is control logic to perform set/reset functions (programmable as synchronous/asynchro-

nous), clock select, chip-select and wider RAM/ROM functions. Figure 2-3 shows an overview of the internal logic

of the slice. The registers in the slice can be conﬁgured for positive/negative and edge/level clocks.

There are 14 input signals: 13 signals from routing and one from the carry-chain (from adjacent slice or PFU).

There are seven outputs: six to routing and one to carry-chain (to adjacent PFU). Table 2-1 lists the signals associ-

ated with each slice.

Slice 0

LUT4 &

CARRY

LUT4 &

CARRY

FF/

Latch

FF/

Latch

Slice 1

LUT4 &

CARRY

LUT4 &

CARRY

Slice 2

LUT4 &

CARRY

LUT4 &

CARRY

From

Routing

Slice 3

LUT4 &

CARRY

LUT4 &

CARRY

FF/

Latch

FF/

Latch

FF/

Latch

FF/

Latch

FF/

Latch

FF/

Latch

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