FPGA
ARCHITECTURE, TIMING, SOFTWARE
Mose Wahlstrom
Lattice Research & Development Team
December 2, 2013
OVERVIEW
Mose Wahlstrom, BSEE OSU 1992
 At Lattice for last 21 years
Excited to enhance partnership between Lattice and OSU
 Will continue to give to OSU (hardware, software, time)
 Will continue to hire (interns and permanent positions)
 Will entertain other guest lectures
Here to focus on FPGA architecture, software, and timing
 Not here to pitch Lattice or recruit. (will be back)
Ask questions!
 (And yell if I use acronyms or unknown terms)
This will go fast and I don’t expect 100% of it to stick.
 Just a general back groud you can build on.
Page: 2
Lattice Semiconductor
TOPICS
Field Programmable Gate Array (FPGA) Architecture (~25 min)
- Top level block diagrams
- Logic building blocks and signal routing
Timing and Power (~15 min)
-
Clocking and control signals
Typical path
Fmax and timing constraints
Static timing analysis (setup/hold and clock to out)
Power consumption
Software Flow (~10 min)
-
Design capture in Verilog, IPexpress
Synthesis into ‘standard’ cells
Cell placement and routing in the FPGA
Bitstream generation and device configuration
Page: 3
Lattice Semiconductor
BLOCK DIAGRAM
FPGAs: An array of PLCs
IO Ring
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
LOGIC
Programmable
Logic Cell (PLC)
Array
-
PLCs align by abutment
Includes both ROUTING and LOGIC
ROUTING tracks cross boundaries
LOGIC is self-contained in the PLC
- The IO ring contains the Input/Outputs
- The IO ring also contains other logic
NOTE: PLC drawn to approximate scale
- ROUTING comprises ~70% of area
- LOGIC comprises ~30% of area
Page: 4
Lattice Semiconductor
MACHXO2 BLOCK DIAGRAM (XO2-1200)
‘Value added’ features in and around the core
On-chip Flash Memory
Provides Instant-on, High
Security & Single Chip
Solution
sysIO Buffers Support
LVCMOS/LVTTL, LVDS
Outputs. I/O Logic Supports
7:1 Output Gearing
User Flash Memory
Embedded Function
Block Hardened SPI,
I2C, Timer/Counter
sysCLOCK PLLs
Frequency Synthesis &
Clock Alignment
sysIO Buffers Support
LVCMOS/LVTTL, and
DDR Memory
Interfaces
sysMEM Block RAM
9Kbit Dual Port
Programmable Function
Units (PFUs) with RAM
sysIO Buffers Support
LVCMOS/LVTTL, LVDS
inputs and PCI. I/O Logic
Supports 7:1 Input Gearing
Flexible Routing
Optimized for Speed, LowCost and Routability
Page: 5
Lattice Semiconductor
BRIEF OVERVIEW OF THE PLC
The Programmable Logic Cell (PLC) is the fundamental building
block of the FPGA Fabric.
The PLC consists of 2 components:
 PFU – Programmable Function Unit (Very simple logic!)
 Programmable Routing Block or Big Switch Box (Muxes)
X6
X2
X6
X2
BSB
(B ig S w itc h B o x )
P FPFU
U /P F F
PLC
Page: 6
Lattice Semiconductor
PFU – PROGRAMMABLE FUNCTION UNIT
Building the PFU from the inside out…
 Nearly all FPGAs are based on a Look-Up-Table plus Register. Most are a LUT4.
Aka LUT4+REG.
 A 4-input LUT is just a 16-bit ROM, with 4 ‘address’ bits (ABCD) and a ‘data’ bit (F).
 By programming the ROM, any 4 input logic functions can be formed.
- Or it can be a simple ROM.
AB
q0
C
q1
(‘q’ values are programmable
SRAM memory bits that are
determined through the
design synthesis process)
LUT Memory
q2
q3
q4
D
q5
q6
q7
q8
F
q9
q10
q11
q12
q13
q14
q15
Page: 7
Lattice Semiconductor
PFU – PROGRAMMABLE FUNCTION UNIT
The Register (Flip-Flop)
 The REG is a custom configurable register with a CLK and Data (D) input
and a Q output.
 The typical register also contains other options such as: Clock Enable
(CE), Set/Reset, Latch mode, and selectable polarities.
 The LUT and register can be used independently, or the output of the LUT
can feed the D input of the register.
 All other PFU logic supports logic expansion and special enhancements
to the LUT+REG.
Early FPGAs were just LUTs and registers!
 (Nearly any logic can be built from just these two blocks.)
Page: 8
Lattice Semiconductor
PFU – SLICE LEVEL VIEW
PFUs are organized into
Slices. They contain:
 Two 4-Input LUTs
 Two Registers
Slice Inputs:
 LUT Inputs: A, B, C, D
 Register Control Inputs:
CLK, CE, LSR
Slice Outputs:
 LUT Outputs: F
 Register Outputs: Q
(More detail Later)
Page: 9
Lattice Semiconductor
PFU – PROGRAMMABLE FUNCTION UNIT
Over time, the PFU has evolved to include other logic to increase
performance and logic density.
 Wider LUTs
- In order to perform wider logic functions with minimal performance hit (no
general routing), special muxes are added to allow wider LUT functions.
- The OFX signal is a muxed output from a pair of LUTs. It is controlled by the
Miscellaneous (M) input. This creates a LUT5 from inputs ABCDM. Five inputs,
32 possible logical combinations.
- Additional OFX muxes support LUT6, LUT7, and LUT8.
 A LUT7 consumes 8 LUT4s (128 memory bits) .
 It also requires 3 additional ‘address’ inputs (M inputs).
 RAM mode
- RAM mode can be implemented by adding some ‘write’ logic to the LUT. This
allows the LUT to implement a small 16 bit RAM. The ‘read’ just functions similar
to ROM/LUT mode. Write requires ‘borrowed’ signals and logic.
 Ripple mode
- Ripple Mode is implemented by adding some additional logic and re-purposing
the LUT bits to function as a carry-look-ahead adder. Ripple mode supports
configurable options for implementing adders, subtractors, and comparators.
Page: 10
Lattice Semiconductor
PFU – PROGRAMMABLE FUNCTION UNIT
Now we put it all together to construct a typical PFU.
 Wide LUT, RAM, and Ripple mode don’t really have any practical uses with a single
LUT. Only when LUTs are grouped together can we build wide logic functions and
multi-bit adders and RAMs. Thus the minimal building blocks need to be more than
just a single LUT+REG.
The ‘SLICE’
 Pairs of LUT+REG are grouped together with extra RAM/Ripple logic to form
SLICEs.
- Some slices only support LUT/ROM mode; others support RAM/Ripple modes.
 Different types of slices are bolted together to form the PFU.
- Ripple and RAM mode are superset slice options.
- All slices can be used as a LUT and/or a REG.
 A Typical PFU contains 4 slices. This would contain/support the following:
- 8 LUT4s or up to a single LUT7, up to a 16x8bit pseudo dual port RAM, an 8 bit
register or shift register, a full 8bit adder/subtractor/comparator, or other
combinations.
Page: 11
Lattice Semiconductor
PFU – SLICE LEVEL VIEW
Each Slice consists of:
 Two 4-Input LUTs
 Two Registers
 Arithmetic Logic circuits
to perform arithmetic
operations
 Circuitry to support
simple RAM mode with
additional input signals
Slice Inputs:
 LUT Inputs: A, B, C, D
 Multi-Purpose Inputs: M
 Fast Carry Input: FCI
 Register Control Inputs:
CLK, CE, LSR
Slice Outputs:
 LUT Outputs: F
 Register Outputs: Q
 Wide Function Outputs:
OFX
 Fast Carry Output: FCO
Page: 12
Lattice Semiconductor
PFU – TOP LEVEL VIEW
A0
B0
C0
D0
M0
CLK0/1
LSR0/1
CE0
LUT4
FCI
A1
B1
C1
D1
M1
LUT4
Arithmetic
Logic
FF/
Latch
FF/
Latch
Slice 0
F0
Q0
OFX0
F1
Q1
OFX1
A2
B2
C2
D2
M2
CLK0/1
LSR0/1
CE1
LUT4
A3
B3
C3
D3
M3
A4
B4
C4
D4
M4
LUT4
LUT4
Arithmetic
Logic
FF/
Latch
A5
B5
C5
D5
M5
LUT4
Arithmetic
Logic
FF/
Latch
FF/
Latch
Slice 1
F2
Q2
OFX2
CLK0/1
LSR0/1
CE2
FF/
Latch
Slice 2
F3
Q3
OFX3
F4
Q4
OFX4
Page: 13
F5
Q5
OFX5
A6
B6
C6
D6
M6
CLK0/1
LSR0/1
CE3
LUT4
A7
B7
C7
D7
M7
LUT4
Arithmetic
Logic
FF/
Latch
FF/
Latch
Slice 3
F6
Q6
OFX6
F7
Q7
OFX7
Lattice Semiconductor
FCO
PFU – SLICE LEVEL VIEW W/CONTROL
FCO
The Slice is controlled
by programmable
SRAM bits.
FXB
FXA
OFX1
1
0
0
LSR
The bits are used to:
 Set LUT ‘q’ bits
Q1
A1
B1
C1
LUT4
 Set Register modes
- Reg or latch
- Set or Reset
D
1
FS1/GEN1
0
1
F/SUM1
D1
 Set Slice to RAM
mode
 Set Slice to Ripple
mode
1
M1
FF_1/
Latch_1
0
Arithmetic
& Carry
Logic
F1
F0
A0
B0
C0
FS0/GEN0
F/SUM0
LUT4
0
1
D0
Q0
0
D
1
FF_0/
Latch_0
M0
0
LSR
1
1
0
OFX0
CE
 Set Slice options
- LSR/CE/CLK
polarities
- Clock and LSR
selection
- Wide LUT modes
LSR0
LSR
LSR1
CLK_DEL
CLK to FF_1
CLK0
CLK to FF_0
CLK1
FCI
Page: 14
Lattice Semiconductor
ADDITIONAL PFU DETAIL
Wide LUTs revisited
 The OFX muxes and the FX/OFX IO signals are dedicated to wider LUT functions.
OFX0 is always a LUT5. OFX1 performs a different function in each slice. Two of the
slices use the OFX1 mux to generate LUT6s from a pair of LUT5s. One slice can then
use OFX1 to generate a LUT7 from the pair of LUT6s. The final OFX1 can be used to
generate a LUT8 from its own LUT7 and that of a neighboring PFU.
 The neighboring LUT7 output/input is one of the few special directly connected
signals that span PFUs.
RAM mode revisited
 Implementing RAM mode requires more signals than are present in a single slice. At
a minimum, a Write Enable (WRE) and a Data Input (DI) are needed. However in order
to support Pseudo Dual Port (PDP) mode, an additional Write Address (WAD) bus is
needed as well as a Write Clock (WCK) for the write port.
 In a typical implementation, these signals come from one of the other slices. For
example, slice 0 and 1 may be used to implement a 16x4 PDP RAM. Slice 2 is
‘burned’ to generate the control signals, which are sent to slice 0/1. And slice 3
doesn’t support RAM mode.
 Thus there are special RAM mode signals sent between slices. These signals are
dedicated for RAM mode and do not leave the PFU.
Page: 15
Lattice Semiconductor
ADDITIONAL PFU DETAIL (CONT.)
Ripple mode revisited
 Ripple mode repurposes a pair of LUTs to implement a full 2-bit Carry Look-Ahead
(CLA) adder. The LUT is programmed as a ROM and slightly modified to produce
Propagate and Generate signals from the (4) inputs and the carry input signal.
 By adding dedicated Fast Carry Input/Output (FCI/FCO) signals, performance is
greatly improved when compared to arithmetic functions using LUT logic and
general routing resources.
 Ripple mode is not a full CLA, but rather a chain of 2-bit CLAs with a dedicated,
rippling fast carry chain.
 Every slice has a FCI and FCO port that connect adjoining slices. At the PFU
boundary, the FCI and FCO connect between neighboring PFUs (typically L to R).
Page: 16
Lattice Semiconductor
PROGRAMMABLE ROUTING BLOCK
ROUTING: (The other three-quarters of the PLC)
 The general purpose routing is not deterministic. It is a collection of
pseudo-random paths. The design software, user preferences, design
congestion, and random seeding all affect the signal routing.
 The routing portion of the PLC can be divided into the signal wires and the
switch boxes that feed them. The wires carry signals from one PLC to
another. The switch boxes are the programmable source connections.
- Once again, the programmable connections are controlled by SRAM bits.
There are two distinct categories of switch boxes.
 Input Switch Boxes (ISBs) are muxes that feed the inputs to the PFU.
Output Switch Boxes (OSBs), are muxes that feed the routing wires out of
the PLC.
 The source for each ISB and OSB is a programmable mux. The inputs to
the mux determine what subset of signal sources can drive that particular
wire or PFU input. A typical routing mux contains about 20 inputs.
 The muxes are typically two stage, one-hot pass-gate muxes.
Page: 17
Lattice Semiconductor
PROGRAMMABLE ROUTING BLOCK
Routing
 In general, the routing wire segments are unidirectional, buffered segments
that span either 2, 3, or 7 PLC blocks (Seg-1, Seg-2, Seg-6 or X1, X2, X6).
- The wires feed both horizontally and vertically in all four directions.
- (X0 wires are an additional special case that are local to a PLC and are really just
an additional layer of connections to enhance routability.)
I0
M0
I1
I2
M1
M2
Mux
Output
M3
I3
Pre-Driver
M0
I4
I5
Driver
M4
To Connect I0 to Mux Output:
Turn ON progammable SRAM
memory cells M0 and M3
M1
M2
Page: 18
Lattice Semiconductor
PROGRAMMABLE ROUTING BLOCK
The BSB contains hundreds of programmable muxes.
 The ISBs feed into the PFU to drive:
- LUT and M inputs
- Clock inputs
- CE and Local Set/Reset inputs
 The OSBs feed out of the PLC:
- OSBs drive all the segment wires (X0, X1, X2, X6)
- The sources for OSB muxes are a pseudo-random selection of both PFU
outputs and other routing wires.
 The following horribly confusing diagram illustrates a high level view of the
routing structure.
- In general, the routing muxes are sparsely populated. Only a small
fraction of the possible wires feeds each ISB or OSB.
- The software must search many possible options to find a route. This
includes swapping LUT inputs, moving logic drivers, and duplicating
logic.
Page: 19
Lattice Semiconductor
PLC ROUTING (CONFUSING DIAGRAM)
8 Seg-1 (28:1 Mux)
32 Seg-2 (16:1 Mux)
16 Seg-6 (16:1 Mux)
Seg-1,-2,-6
From Adj PFUs
(all 4 directions)
Seg-1,-2,-6 To Adj PFUs
(all 4 directions)
Output Switch Boxes
(Seg-0, Seg-1, Seg-2, Seg-6)
8F + 8Q + 8OFX
Seg-1
Seg-2
8 Seg-0 (20:1 Mux)
Seg-0
8F + 8Q
PFU
Input Switch Boxes
52 Buffered, 2-Stage Muxes
8 LUT
Arithmetic
Wide Gating
32 LUT ISB (25:1 Mux)
8 M ISB (16:1 Muxes)
4 CLK ISB (29:1 Mux)
4 CE ISB (21:1 Mux)
4 LSR ISB (21:1 Mux)
Control
8 FF
Muxn, Din
Global
Clk/Cntl
Page: 20
Lattice Semiconductor
PLC ROUTING CONNECTIVITY
Example: LUT ISB Mux connectivity
 CE, LSR, CLK are similar but include global clock resources
 Directs are local:
- F/Q of local PFU
- F for wider logic
- Q for Counters, State
machines
 Others inputs are from
general routing.
To PFU LUT Inputs (A,B,C,D)
and M
 The mux controls are set
static by SRAM
programming bits
Page: 21
Lattice Semiconductor
PLC ROUTING CONNECTIVITY
Example: X1 ‘Output’ Mux connectivity
2 X6
2 X2
8
F [7 :0 ]
Q [7 :0 ]
O F X [7 :0 ]
X2
8
8
X6
X6
M
ux
25
2:1
5 :1
Col n
Col n+1
X2
M ux
X2
IS B s
Mux controls are
static SRAM
2 X6
2 X2
(Similar for X2, X6 and even the local X0, however not limited to just
PFU outputs. X2/X6/X0 primarily source other routing resources)
Page: 22
Lattice Semiconductor
PLC ROUTING CONNECTIVITY
The Hierarchical Routing Connectivity Concept
SLICE 0
X6
X2
Bank 0
Bank 0
X0
Type1
LUTISB
A0
LUTISB
B0
LUT 0
X0
Type2
X0
Type3
LUTISB
C0
LUTISB
D0
LUTISB
A1
LUTISB
B1
LUTISB
C1
LUTISB
D1
Similar to a system of roads:
 Expressways with limited off ramps
 Local highways
 Neighborhood streets
Page: 23
LUT 1
Lattice Semiconductor
GLOBAL ROUTING (CLOCK TIMING)
In addition to the general purpose routing, there are some global control
signals that feed the entire PLC array and the peripheral logic in the IO ring.
 The most important global signals are the clock signals. (Synchronous logic)
- All FPGA devices contain clock ‘trees’ to guarantee all registers receive the clock
at essentially the same time to provide deterministic setup and hold times between
registers. This is known as the primary clock tree, which has many branches and
programmable options for clock gating, switching, and power control.
- All clock signal trees have special routing mux resources to choose their sources.
These muxes are located in the central clock switch.
- The sources for the clocking resources are a mix of general purpose routing,
dedicated IO pins, Phase Lock Loop (PLL) outputs, and other clock resources.
This allows the implementation of complex clock systems with both internal and
external clocks, multiple clock frequencies, and various clock phases.
 All devices have a Global Set Reset (GSR). This signal fans out to every register in
the device, both in the PLC array and in the IO ring. This provides a system reset.
 From a user’s perspective, these are the only significant global signals. However
there are lots of other global signals dedicated to programming, power control, etc.
Page: 24
Lattice Semiconductor
CLOCK TREE
IO Ring
Clock trees guarantee
identical clock delay to
all registers.
REG
CENTRAL
CLOCK
SWITCH
…
REG
…
 This includes PLC
registers and IO ring IP
blocks such as IO cells
and embedded RAM.
 There are many parallel
clock trees to support
multiple clock
domains.
 The software controls
all timing
- PFU to PFU
- PFU to IO ring
- PFU to IP block
- IP block to PFU
Clock Input Source
Page: 25
Lattice Semiconductor
TYPICAL SIGNAL PATH
Typical Path:
 A 4-logic-level deep register-to-register path
Routing delay
Q
FF
PFU
CLK2Q
Routing
+ ISB
Routing delay
A
Routing
+ ISB
LUT
PFU
LUT4 delay
Routing delay
D
Routing
+ ISB
LUT
PFU
LUT4 delay
Routing delay
A
Routing
+ ISB
LUT
PFU
LUT4 delay
D
LUT
FF
PFU
LUT4_delay
+
FF Setup
Path Delay = (CLK2Q + LUT4 delays + FF_Setup) + (OSB Routing + ISB)
The routing delays could represent local intra-PLC delays, or they could be inter-PLC delays
crossing the entire PLC array.
(Not shown is the clock signal, which also has a delay.)
Page: 26
Lattice Semiconductor
SOFTWARE TIMING CONTROL
All routing structures, PFU logic elements and peripheral IP blocks require
specific timings in order to function correctly. There are three basic timing
constructs: FMAX, routing delays, and Port Timings.
FMAX (Maximum Operating Frequency)
 IP blocks, PFU modes, and clock trees all have an explicit FMAX
- A Block RAM may have an FMAX of 300MHZ, beyond which read or write
functional will fail to execute correctly.
- An LVCMOS IO standard may have an FMAX of 250MHZ, beyond which
the high and low output level would be violated.
- These FMAX values are determined by simulation of the design (Lattice
Spice sims), by characterization, or by ‘binning’ at final test.
- The FMAX values are provided to the software to limit a users allowed
operating frequency.
 The sum of the routing delays between registers can also determine a
‘design specific’ maximum operating frequency.
- Every signal path (route) in a user’s design has a specific delay.
- There is usually a very small fraction of routes (or even a single route)
that may also limit the maximum operating frequency.
 Users enter their desired operating frequency and the software checks to
make sure that all blocks and resources meet the FMAX constraints.
Page: 27
Lattice Semiconductor
SOFTWARE TIMING CONTROL (CONT.)
Routing Delays and Port Timings
 All synchronous blocks require specific Setup/Hold time (TSU/TH) on IN
ports and they provide specific Clock To Out (TCO) on OUT ports.
- These TSU/TH/TCO values are determined by simulation of the device,
by characterization, or by ‘binning’ at final test.
 The routing delays of each wire and mux type (X2, X6, ISB, OSB) are also
simulated and characterized.
 All these port and routing timings are integrated into the software so that it
can determine timing closure on every signal path between register.
 For the software to be effective, users must enter timing ‘constraints’.
- This sets FMAX and prioritizes internal requirements (general goals).
 External IO requirements must also be provided (TSU/TH/TCO).
- These are determined by off-chip clock and data alignments, such as
from an external memory, interface chip, or processor.
 With all of the above information, the software attempts to meet all static
timing requirements. It has many options such as:
- Moving logic (registers) closer together to fix a Setup time violation.
- Intentionally adding delay to a route to fix a Hold time violation.
- Duplicating logic closer to a destination to fix a setup time violation.
- Giving up.
Page: 28
Lattice Semiconductor
FPGA POWER CONSUMPTION
The software can also estimate power consumption.
 Similar to the timing, the power data comes from many sources such as:
Spice simulations, characterization, and final test ‘binning’.
Power data is integrated into the software for each routing element,
PFU mode, and IP block. There are two basic components of power,
DC and AC power.
DC power consumption:
- DC power is comprised of static bias currents and leakage.
- The leakage currents are calculated from a curve fit equation based on
-
supply voltage (VCC), Temperature, and process variation (typical or
worst-case). The software provides users the means to enter VCC and
temperature as well as select the process.
Every LUT, Block RAM, routing wire, etc. has different bias and leakage.
There are also different calculations based on if an element is used or
unused in a particular user’s design.
The software will also generate statistical averages when logic values
affect DC bias or leakage current (a ‘1’ and ‘0’ may be different).
Page: 29
Lattice Semiconductor
FPGA POWER CONSUMPTION (CONT.)
AC power consumption:
 For routing, only a function of:
- Capacitance (extracted from layout, technology, and simulation)
- Voltage (Provided by customer’s design)
- Frequency (average switching frequency of each ‘wire’)
 Every ‘wire’ will switch at different rates depending on the design,
activity, and time slice.
 Activity Factor (AF) is provided by the customer as an average
indicator of switching rates (0%-100%)
 For the PFU logic and other IP blocks
- The same CVF method can be used. ‘Capacitance’ values are provided in
the software for each IP block.
- Users must enter the clock frequency for each clock that feeds the PFUs
and IP blocks.
Total Power:
 Total power is the summation of ‘used’ DC, ‘unused’ DC, and AC CVF.
- Every routing, PFU, and IP element is separately calculated and summed
together to produce the total power for the entire FPGA.
- Every supply is analyzed separately.
Page: 30
Lattice Semiconductor
SOFTWARE FLOW
‘ispLEVER’ is the old name
for the Diamond software.
Customer Entry
IPExpress
 Users capture their design,
usually with Verilog and
other GUI and file inputs.
Preference File
Verilog / VHDL
Source
 Synthesis turns Verilog
into ‘standard cells’ that
are the fundamental
building blocks of logic:
- Logic equations,
registers, adders,
memory, etc.
- This step is pretty much
voodoo to me.
- Lattice provides
architectural info to
Synopsys.
Verilog / VHDL
Source
ispLEVER
Front-End
Synthesis
(3rd Party Tool)
Other conversions
Map
.NCL
(Unrouted)
ncd2ncl
.NCD
(Unrouted)
ncl2ncd
Page: 31
Place and Route
(PAR)
ispLEVER
Back-End
Lattice Semiconductor
SOFTWARE FLOW (CONT.)
Synthesis
(3rd Party Tool)
 The logical building blocks are then
‘mapped’ to FPGA specific resources
such as:
- LUTs, Block RAMs, ripple adders, PLLs,
etc.
 All of the logic elements are then ‘placed’
into appropriate sites in the FPGA.
- LUT equations are placed in Slices.
- RAMs in Block RAM locations.
- If the device runs out of resources, it
will try to remap some of the elements,
or it will ultimately fail.
 All of the logic elements are then ‘placed’
into appropriate sites in the FPGA.
- LUTs are placed in specific Slices, etc.
 Once placed, all signals are then routed.
- The software can rearrange placement
if it encounters routing limitations.
- Some designs will fail to route.
 The final step is ‘bitstream’ generation.
- This process sets all of the
programmable SRAM bits to implement
the logic and routing in the design
 The bitstream is then loaded into the
device SRAM bits to implement the
user’s function. (Or into Flash Memory)
Other conversions
Map
.NCL
(Unrouted)
ncd2ncl
.NCD
(Unrouted)
ncl2ncd
ispLEVER
Back-End
Place and Route
(PAR)
.NCL
(Routed)
ncd2ncl
.NCD
(Routed)
ncl2ncd
Bitgen
.RBT
(or .JED or .BIT)
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OTHER
I believe all of these tools are available in the free software.
EPIC (don’t know this acronym)
 EPIC is a GUI tool included in the software that can be used to view,
analyze and design nearly every aspect of the FPGA.
- It shows every routing segment, LUT, IP block, etc.
- It is very cumbersome and difficult to learn.
NCL
 The software can also generate an NCL (NeoCad Listing?), which is a text
version of the design files that the Map, Place, and Route tools operate on.
- Once again, very cryptic and difficult to learn. But it is a text
representation of an entire user’s design with all routing and logic.
Power Calculator
 Can be used to estimate FPGA power consumption.
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