Data Sheet
June 1999
ORCA
Series 3C and 3T 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 seg-
ments. The switching circuitry connects the routing
segments, 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
routing segments, connected by switching circuitry
called 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 routing segments uses
three basic types of switching circuits: two types of con-
figurable interconnect points (CIPs) and bidirectional
buffers (BIDIs). The basic element in CIPs is one or
more pass transistors, each controlled by a configura-
tion RAM bit. The two types of CIPs are the mutually
exclusive (or multiplexed) 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 18
shows an example of both types of CIPs.
3-Statable Bidirectional Buffers
Bidirectional buffers, previously described in the SLIC
section of the programmable logic cell discussion, pro-
vide isolation as well as amplification for signals routed
a long distance. Bidirectional buffers are also used to
route signals diagonally in the PLC (described later in
the subsection entitled Intra-PLC Routing), and BIDIs
can be used to indirectly route signals through the
switching routing (xSW) segments. Any number from
zero to ten BIDIs can be used in a given PLC.
B
A
INDEPENDENT CIP
=
A
CD
B
MULTIPLEXED CIP
CD
O
2
A
B
C
A
B
C
O
Key: C = configuration data.
5-5973(C)
Figure 18. Configurable Interconnect Point
Lucent Technologies Inc.
27
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