
Lucent Technologies Inc.
5
Data Sheet
June 1999
ORCA Series 2 FPGAs
ORCA
 Foundry
 Development System 
Overview
The ORCA Foundry Development System interfaces to 
front-end design entry tools and provides the tools to 
produce a configured FPGA. In the design flow, the 
user defines the functionality of the FPGA at two 
points: at design entry and at the bit stream generation 
stage. 
Following design entry, the development system’s map, 
place, and route tools translate the netlist into a routed 
FPGA. Its bit stream generator is then used to generate 
the configuration data which is loaded into the FPGA’s 
internal configuration RAM. When using the bit stream 
generator, the user selects options that affect the func-
tionality of the FPGA. Combined with the front-end 
tools, ORCAFoundry produces configuration data that 
implements the various logic and routing options dis-
cussed in this data sheet.
Architecture
The ORCASeries FPGA is comprised of two basic 
elements: PLCs and PICs. Figure 1 shows an array of 
programmable logic cells (PLCs) surrounded by pro-
grammable input/output cells (PICs). The Series 2 has 
PLCs arranged in an array of 20 rows and 20 columns. 
PICs are located on all four sides of the FPGA between 
the PLCs and the IC edge. 
The location of a PLC is indicated by its row and col-
umn so that a PLC in the second row and third column 
is R2C3. PICs are indicated similarly, with PT (top) and 
PB (bottom) designating rows and PL (left) and PR 
(right) designating columns, followed by a number. The 
routing resources and configuration RAM are not 
shown, but the interquad routing blocks (hIQ, vIQ) 
present in the Series 2 series are shown. 
Each PIC contains the necessary I/O buffers to inter-
face to bond pads. The PICs also contain the routing 
resources needed to connect signals from the bond 
pads to/from PLCs. The PICs do not contain any user-
accessible logic elements, such as flip-flops.
Combinatorial logic is done in look-up tables (LUTs) 
located in the PFU. The PFU can be used in different 
modes to meet different logic requirements. The LUT’s 
configurable medium-/large-grain architecture can be 
used to implement from one to four combinatorial logic 
functions. The flexibility of the LUT to handle wide input 
functions, as well as multiple smaller input functions, 
maximizes the gate count/PFU. 
The LUTs can be programmed to operate in one of 
three modes: combinatorial, ripple, or memory. In com-
binatorial mode, the LUTs can realize any four-, five-, 
or six-input logic functions. In ripple mode, the high-
speed carry logic is used for arithmetic functions, the 
new multiplier function, or the enhanced data path 
functions. In memory mode, the LUTs can be used as a 
16 x 4 read/write or read-only memory (asynchronous 
mode or the new synchronous mode) or a new 16 x 2 
dual-port memory.
Programmable Logic Cells
The programmable logic cell (PLC) consists of a pro-
grammable function unit (PFU) and routing resources. 
All PLCs in the array are identical. The PFU, which con-
tains four LUTs and four latches/FFs for logic imple-
mentation, is discussed in the next section.
Programmable Function Unit
The PFUs are used for logic. Each PFU has 19 exter-
nal inputs and six outputs and can operate in several 
modes. The functionality of the inputs and outputs 
depends on the operating mode. 
The PFU uses three input data buses (A[4:0], B[4:0], 
WD[3:0]), four control inputs (C0, CK, CE, LSR), and a 
carry input (CIN); the last is used for fast arithmetic 
functions. There is a 5-bit output bus (O[4:0]) and a 
carry-out (COUT). 
5-2750(F).r3
Figure 2. PFU Ports
PROGRAMMABLE LOGIC CELL (PLC)
WD3
WD2
WD1
WD0
A4
A3
A2
A1
A0
B4
B3
B2
B1
B0
O4
O3
O2
O1
O0
PROGRAMMABLE
FUNCTION UNIT
(PFU)
CE LSR
C0 CK
(ROUTING RESOURCES, CONFIGURATION RAM)
CIN
COUT