
Lucent Technologies Inc.
17
Data Sheet
June 1999
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.
 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 con-
figured 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.
2
INDEPENDENT CIP
CD
A
B
A
B
=
MULTIPLEXED CIP
A
B
C
A
B
C
O
O
CD