LFECP3E-5F900C 查看數據表（PDF） - Lattice Semiconductor

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LFECP3E-5F900C

LatticeECP/EC Family Data Sheet Introduction

Lattice Semiconductor 

Lattice Semiconductor

Architecture

LatticeECP/EC Family Data Sheet

Modes of Operation

Each Slice is capable of four modes of operation: Logic, Ripple, RAM and ROM. The Slice in the PFF is capable of

all modes except RAM. Table 2-2 lists the modes and the capability of the Slice blocks.

Table 2-2. Slice Modes

PFU Slice

PFF Slice

Logic

LUT 4x2 or LUT 5x1

LUT 4x2 or LUT 5x1

Ripple

2-bit Arithmetic Unit

2-bit Arithmetic Unit

RAM

SPR16x2

N/A

ROM

ROM16x1 x 2

ROM16x1 x 2

Logic Mode: In this mode, the LUTs in each Slice are configured as 4-input combinatorial lookup tables. A LUT4

can have 16 possible input combinations. Any logic function with four inputs can be generated by programming this

lookup table. Since there are two LUT4s per Slice, a LUT5 can be constructed within one Slice. Larger lookup

tables such as LUT6, LUT7 and LUT8 can be constructed by concatenating other Slices.

Ripple Mode: Ripple mode allows the efficient implementation of small arithmetic functions. In ripple mode, the fol-

lowing functions can be implemented by each Slice:

• Addition 2-bit

• Subtraction 2-bit

• Add/Subtract 2-bit using dynamic control

• Up counter 2-bit

• Down counter 2-bit

• Ripple mode multiplier building block

• Comparator functions of A and B inputs

- A greater-than-or-equal-to B

- A not-equal-to B

- A less-than-or-equal-to B

Two additional signals: Carry Generate and Carry Propagate are generated per Slice in this mode, allowing fast

arithmetic functions to be constructed by concatenating Slices.

RAM Mode: In this mode, distributed RAM can be constructed using each LUT block as a 16x1-bit memory.

Through the combination of LUTs and Slices, a variety of different memories can be constructed.

The Lattice design tools support the creation of a variety of different size memories. Where appropriate, the soft-

ware will construct these using distributed memory primitives that represent the capabilities of the PFU. Table 2-3

shows the number of Slices required to implement different distributed RAM primitives. Figure 2-5 shows the dis-

tributed memory primitive block diagrams. Dual port memories involve the pairing of two Slices, one Slice functions

as the read-write port. The other companion Slice supports the read-only port. For more information on using RAM

in LatticeECP/EC devices, please see details of additional technical documentation at the end of this data sheet.

Table 2-3. Number of Slices Required For Implementing Distributed RAM

SPR16x2 DPR16x2

Number of slices

1

2

Note: SPR = Single Port RAM, DPR = Dual Port RAM

2-5

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