LFEC10 datasheet(18/163 Pages) LATTICE

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2-15

Architecture

Lattice Semiconductor

LatticeECP/EC Family Data Sheet

decoders. These complex signal processing functions use similar building blocks such as multiply-adders and mul-

tiply-accumulators.

sysDSP Block Approach Compared to General DSP

Conventional general-purpose DSP chips typically contain one to four (Multiply and Accumulate) MAC units with

ﬁxed data-width multipliers; this leads to limited parallelism and limited throughput. Their throughput is increased by

higher clock speeds. The LatticeECP, on the other hand, has many DSP blocks that support different data-widths.

This allows the designer to use highly parallel implementations of DSP functions. The designer can optimize the

DSP performance vs. area by choosing an appropriate level of parallelism. Figure 2-18 compares the serial and the

parallel implementations.

Figure 2-18. Comparison of General DSP and LatticeECP-DSP Approaches

sysDSP Block Capabilities

The sysDSP block in the LatticeECP-DSP family supports four functional elements in three 9, 18 and 36 data path

widths. The user selects a function element for a DSP block and then selects the width and type (signed/unsigned)

of its operands. The operands in the LatticeECP-DSP family sysDSP Blocks can be either signed or unsigned but

not mixed within a function element. Similarly, the operand widths cannot be mixed within a block.

The resources in each sysDSP block can be conﬁgured to support the following four elements:

• MULT

(Multiply)

• MAC

(Multiply, Accumulate)

• MULTADD

(Multiply, Addition/Subtraction)

• MULTADDSUM (Multiply, Addition/Subtraction, Accumulate)

The number of elements available in each block depends on the width selected from the three available options x9,

x18, and x36. A number of these elements are concatenated for highly parallel implementations of DSP functions.

Table 2-1 shows the capabilities of the block.

Multiplier 0

Operand

Multiplier 1

Multiplier

(k-1)

Accumulator

Output

m/k

loops

Single

Multiplier

Operand

Accumulator

Operand

M loops

Function implemented in

General purpose DSP

Function implemented

in LatticeECP

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