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Datapath libraries
There are two kinds of datapath libraries:
- dplib is a cell library dedicated to high density data-paths.
It must be used in conjunction with the data-path tools
fpgen and dpr.
The cells in dplib have the same functionnalities as the
ones in sclib, but have a topology that is usable only
within a datapath.
Scmap can also map a behavior onto the dplib
library.
- fplib is a set of above 30 regular functions that are
useful in the design of a datapath.
These functions range from a n inputs nand gate to
a n
m register file.
Here the cells share the power and ground lines in metal2.
A powerful dedicated over the cell router can route custom
blocks and logic glue in the same structure.
Among the fplib functionnalities, four optimized blocks
generators should be presented in more details, as they reflect the
quality of this library.
All the generators are build with a tiler using a dedicated leaf cell
library.
Their output is a symbolic layout, a VHDL behavior, a set of
pattern for test purpose, a netlist, an icon, and a datasheet
indicating size and timing estimation for a given technology.
The structural parameters varies according to their functionalities.
- optimized generators for datapath operators:
- rsa ,
- a fast adder generator, with propagation time
in log nb and size in nb log nb,
where nb is the number of bits.
Its has 2 or 3 input buses, and if needed a carry input.
It may be used as a substractor or adder/substractor.
Params |
Meaning |
Range |
nb |
number of bits |
3 to 128 |
cin |
carry in |
true or false |
csa |
three inputs adder |
true or false |
ovr |
overflow flag |
true or false |
- rfg ,
- a static register file generator.
It has one write address , and one or two read address.
It may be operated as a set of level-sensitive latches
or edge triggered flip-flops.
Params |
Meaning |
Range |
nb |
number of bits |
2 to 64 |
nw |
number of words |
2 to 256 |
bus |
number of read bus |
1 or 2 |
op |
mode of operation |
latch or flip-flop |
low power |
reduce power consumption |
true or false |
- bsg ,
- a barrel shifter generator.
Possible operations are :
- logical right shift
- arithmetical right shift
- logical left shift
- arithmetical left shift
- right rotation
- left rotation
Params |
Meaning |
Range |
nb |
number of bits |
3 to 64 |
- amg ,
- an integer modified booth algorithm array
multiplier.
the x and y inputs are independent,
and pipeline stages can be inserted in the circuit.
Params |
Meaning |
Range |
nx |
number of bits of the x operand |
8 to 64 |
ny |
number of bits of the y operand |
8 to 64 |
ps |
number of pipeline stages to be inserted in the
circuit |
0 to min(
,
)-1 |
Next: Custom libraries
Up: Cell libraries
Previous: Standard cell library
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