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OR2C04A

ORCA® Series 2 Field-Programmable Gate Arrays

Lattice Semiconductor 

Data Sheet

January 2002

ORCA Series 2 FPGAs

Programmable Logic Cells (continued)

PLC Routing Resources

Generally, the ORCA Foundry Development System is

used to automatically route interconnections. Interac-

tive routing with the ORCA Foundry design editor

(EPIC) is also available for design optimization. To use

EPIC for interactive layout, an understanding of the

routing resources is needed and is provided in this sec-

tion.

The routing resources consist of switching circuitry and

metal interconnect segments. Generally, the metal

lines which carry the signals are designated as routing

nodes (lines). The switching circuitry connects the rout-

ing nodes, providing one or more of three basic func-

tions: signal switching, amplification, and isolation. A

net running from a PFU or PIC output (source) to a

PLC or PIC input (destination) consists of one or more

lines, connected by switching circuitry designated as

configurable interconnect points (CIPs).

The following sections discuss PLC, PIC, and interquad

routing resources. This section discusses the PLC

switching circuitry, intra-PLC routing, inter-PLC routing,

and clock distribution.

Configurable Interconnect Points

The process of connecting lines uses three basic types

of switching circuits: two types of configurable intercon-

nect points (CIPs) and bidirectional buffers (BIDIs). The

basic element in CIPs is one or more pass transistors,

each controlled by a configuration RAM bit. The two

types of CIPs are the mutually exclusive (or multi-

plexed) CIP and the independent CIP.

A mutually exclusive set of CIPs contains two or more

CIPs, only one of which can be on at a time. An inde-

pendent CIP has no such restrictions and can be on

independent of the state of other CIPs. Figure 19

shows an example of both types of CIPs.

INDEPENDENT CIP

B

A

=

CD

A

B

MULTIPLEXED CIP

O

A

CD

2

A

B

B

O

C

C

f.13(F)

Figure 19. Configurable Interconnect Point

3-Statable Bidirectional Buffers

Bidirectional buffers provide isolation as well as amplifi-

cation for signals routed a long distance. Bidirectional

buffers are also used to drive signals directly onto

either vertical or horizontal XL and XH lines (to be

described later in the inter-PLC routing section). BIDIs

are also used to indirectly route signals through the

switching lines. Any number from zero to eight BIDIs

can be used in a given PLC.

The BIDIs in a PLC are divided into two nibble-wide

sets of four (BIDI and BIDIH). Each of these sets has a

separate BIDI controller that can have an application

net connected to its TRI input, which is used to 3-state

enable the BIDIs. Although only one application net

can be connected to both BIDI controllers, the sense of

this signal (active-high, active-low, or ignored) can be

configured independently. Therefore, one set can be

used for driving signals, the other set can be used to

create 3-state buses, both sets can be used for 3-state

buses, and so forth.

Lattice Semiconductor

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