OR4 datasheet(20/152 Pages) LATTICE

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Lattice Semiconductor

Data Sheet

May, 2006

ORCA Series 4 FPGAs

Programmable Logic Cells (continued)

5-5749(F)

Figure 13. Memory Mode Expansion Example—128x8 RAM

RD[7:0]

WA[6:0]

RA[6:0]

CLK

WPE 1

WPE 2

WD[7:4]

PLC

WD[7:0]

WPE 1

WPE 2

RD[3:0]

WD[3:0]

PLC

RD[7:4]

WPE 1

WPE 2

WD[7:4]

PLC

WPE 1

WPE 2

RD[3:0]

WD[3:0]

PLC

RD[7:4]

Supplemental Logic and Interconnect Cell

Each PLC contains a SLIC embedded within the PLC

routing, outside of the PFU. As its name indicates, the

SLIC performs both logic and interconnect (routing)

functions. Its main features are 3-statable, bidirectional

buffers, and a PAL-like decoder capability. Figure 14

shows a diagram of a SLIC with all of its features

shown. All modes of the SLIC are not available at one

time.

The ten SLIC inputs can be sourced directly from the

PFU or from the general routing fabric. SI[0:9] inputs

can come from the horizontal or vertical routing and

I[0:9} comes from the PFU outputs O[9:0]. These inputs

can also be tied to a logical 1 or 0 constant. The inputs

are twin-quad in nature and are segregated into two

groups of four nibbles and a third group of two inputs

for control. Each input nibble groups also have

3-state capability, however the third pair does not.

There is one 3-state control (TRI) for each SLIC, with

the capability to invert or disable the 3-state control for

each group of four BIDIs. Separate 3-state control for

each nibble-wide group is achievable by using the

SLICs decoder (DEC) output, driven by the group of

two BIDIs, to control the 3-state of one BIDI nibble

while using the TRI signal to control the 3-state of the

other BIDI nibble. Figure 15 shows the SLIC in buffer

mode with available 3-state control from the TRI and

DEC signals. If the entire SLIC is acting in a buffer

capacity, the DEC output may be used to generate a

constant logic 1 (VHI) or logic 0 (VLO) signal for general

use.

The SLIC may also be used to generate PAL-like AND-

OR with optional INVERT (AOI) functions or a decoder

of up to 10 bits. Each group of buffers can feed into an

AND gate (4-input AND for the nibble groups and

2-input AND for the other two buffers). These AND

gates then feed into a 3-input gate that can be conﬁg-

ured as either an AND gate or an OR gate. The output

of the 3-input gate is invertible and is output at the DEC

output of the SLIC. Figure 19 shows the SLIC in full

decoder mode.

The functionality of the SLIC is parsed by the two nib-

ble-wide groups and the 2-bit buffer group. Each of

these groups may operate independently as BIDI buff-

ers (with or without 3-state capability for the nibble-

wide groups) or as a PAL/decoder.

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