prjxray/docs/architecture/glossary.rst

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Glossary
========================
.. glossary::
BEL
BLE
Basic element (BEL) or basic logic element (BLE)
BELs or BLEs are the basic logic elements in an FPGA, including
carry or fast adders (CFAs), flip flops (FFs), lookup tables (LUTs),
multiplexers (MUXes), and other element types.
Note: Programmable interconnects (PIPs) are not counted as BELs.
BELs come in two forms:
* Basic BEL - A logic unit which does things.
* Routing BEL - A unit which is statically configured at routing time.
Bitstream
Binary data that is directly loaded into an FPGA to perform configuration.
Contains configuration :term:`frames <frame>` as well as programming
sequences and other commands required to load and activate same.
Clock domain
Portion of a :term:`horizontal clock row` to one side of the global clock
spine. Often refers to :term:`tiles <tile>` that are associated with these
clocks.
Column
A term used in :term:`bitstream` configuration to denote
a collection of :term:`tiles <tile>`, physically organized as
a vertical line, and configured by the same set of configuration frames.
Logic columns span 50 tiles vertically and 2 tiles horizontally
(pairs of logic tiles and interconnect tiles).
CLB
Configurable logic block (CLB)
The configurable logic unit of an FPGA. Also called a **logic cell**.
A CLB is a combination of basic logic elements (:term:`BELs <BEL>`).
Database
A term used in *Project X-Ray* to denote
text files containing meaningful labels for bit positions within
:term:`segments <segment>`.
Frame
The fundamental unit of :term:`bitstream` configuration data consisting of
101 :term:`words <word>`.
Each frame has a 32-bit frame address and 101 payload words, 32 bits each.
The 50th payload words is an EEC.
The 7 LSB bits of the frame address are the frame index within the
configuration :term:`column` (called *minor frame address* in the Xilinx
documentation). The rest of the frame address identifies the configuration
column (called *base frame address* in Project X-Ray nomenclature).
The bits in an individual frame are spread out over the entire column.
For example, in a logic column with 50 tiles, the first tile is configured
with the first two words in each frame, the next tile with the next two
words, and so on.
Frame base address
The first configuration frame address for a :term:`column`. A frame base
address has always the 7 LSB bits cleared.
Fuzzer
Scripts and a makefile to generate one or more :term:`specimens <specimen>`
and then convert the data from those specimens into a :term:`database`.
Half
Portion of a device defined by a virtual line dividing the two sets of global
clock buffers present in a device. The two halves are referred to as
the top and bottom halves.
Node
A routing node on the device. A node is a collection of :term:`wires <wire>`
spanning one or more "tiles"term" `tiles <tile>`.
Nodes that are local to a tile map 1:1 to a wire. A node that spans multiple
tiles maps to multiple wires, one in each tile it spans.
PIP
Programmable interconnect point (PIP)
Connection point between two wires in a tile that may be enabled or
disabled by the configuration.
Horizontal clock row
Portion of a device including 12 horizontal clocks and the 50 interconnect
and function tiles associated with them. A :term:`half` contains one or
more horizontal clock rows and each half may have a different number of
rows.
ROI
Region of interest (ROI)
A term used in *Project X-Ray* to denote a
rectangular region on the FPGA that is the current focus of our study.
Right now this is `SLICE_X12Y100:SLICE_X27Y149` on a `xc7a50tfgg484-1`
chip.
Segment
All configuration bits for a horizontal slice of a :term:`column`.
This corresponds to two ranges: a range of :term:`frames <frame>`
and a range of :term:`words <word>` within frames. A segment of a logic
column is 36 frames wide and 2 words high.
Site
Portion of a tile where :term:`BELs <BEL>` can be placed. The
:term:`slices <slice>` in a :term:`CLB` tile are sites.
Slice
Portion of a :term:`tile` tile that contains :term:`BELs <BEL>`.
A `CLBLL_L/CLBLL_R` tile contains two `SLICEL` slices.
A `CLBLM_L/CLBLM_R` tile contains one `SLICEL` slice and one `SLICEM` slice.
Specimen
A :term:`bitstream` of a (usually auto-generated) design with additional
files containing information about the placed and routed design.
These additional files are usually generated using Vivado TCL scripts
querying the Vivado design database.
Tile
Fundamental unit of physical structure containing a single type of
resource or function. A container for :term:`sites <site>` and
:term:`slices <slice>`. The whole chip is a grid of tiles.
The most important tile types are left and right interconnect tiles
(`INT_L` and `INT_R`) and left and right :term:`CLB` logic/memory tiles
(`CLBLL_L`, `CLBLL_R`, `CLBLM_L`, `CLBLM_R`).
Wire
Physical wire within a :term:`tile`.
Word
32 bits stored in big-endian order. Fundamental unit of :term:`bitstream`
format.