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/trunk/pdchain.vhdl
0,0 → 1,49
--
-- * pipelined synchronous pulse counter *
-- pdchain -- multi-bit counter top-level entity
--
-- fast counter for slow-carry architectures
-- non-monotonic counting, value calculable by HDL/CPU
--
-- idea&code by Marek Peca <mp@duch.cz> 08/2012
-- Vyzkumny a zkusebni letecky ustav, a.s. http://vzlu.cz/
-- thanks to Michael Vacek <michael.vacek@vzlu.cz> for testing
--
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
entity pdchain is
generic (
n: natural := 32
);
port (
clock: in std_logic;
en: in std_logic;
q: out std_logic_vector (n-1 downto 0)
);
end pdchain;
 
architecture behavioral of pdchain is
component pdivtwo
port (
clock: in std_logic;
en: in std_logic;
q, p: out std_logic
);
end component;
--
signal b: std_logic_vector (q'range);
begin
q0: pdivtwo
port map (
clock => clock, en => en, p => b(0), q => q(0)
);
ch: for k in 1 to b'high generate
qk: pdivtwo
port map (
clock => clock, en => b(k-1), p => b(k), q => q(k)
);
end generate;
end behavioral;
/trunk/doc/pcounter_sch.pdf Cannot display: file marked as a binary type. svn:mime-type = application/octet-stream
trunk/doc/pcounter_sch.pdf Property changes : Added: svn:mime-type ## -0,0 +1 ## +application/octet-stream \ No newline at end of property Index: trunk/doc/pcounter_4bit_trace.pdf =================================================================== Cannot display: file marked as a binary type. svn:mime-type = application/octet-stream Index: trunk/doc/pcounter_4bit_trace.pdf =================================================================== --- trunk/doc/pcounter_4bit_trace.pdf (nonexistent) +++ trunk/doc/pcounter_4bit_trace.pdf (revision 2)
trunk/doc/pcounter_4bit_trace.pdf Property changes : Added: svn:mime-type ## -0,0 +1 ## +application/octet-stream \ No newline at end of property Index: trunk/doc/README =================================================================== --- trunk/doc/README (nonexistent) +++ trunk/doc/README (revision 2) @@ -0,0 +1,85 @@ +-- +-- * pipelined synchronous pulse counter * +-- +-- fast counter for slow-carry architectures +-- non-monotonic counting, value calculable by HDL/CPU +-- +-- idea&code by Marek Peca 08/2012 +-- Vyzkumny a zkusebni letecky ustav, a.s. http://vzlu.cz/ +-- thanks to Michael Vacek for testing +-- + +Pipelined Synchronous Pulse Counter +=================================== + +is a proposal of binary counter, designed to minimize logic path +length in between flip-flops to one gate (MUX/AND) only, at the +expense of not so straightforward binary counting. The reason for this +design has emerged while using Actel (MicroSemi) ProASIC/IGLOO +architecture, lacking any hardwired support for fast carry. + +During our work on Actel FPGAs (basically, 3-LUT & DFF only), we were +aware of following types of faster counters: +- LFSR counter +- Johnson counter +- "RLA counter" (as tailored using Actel's SmartGen core generator) + +Johnson due to its O(2^n) (n as number of bits) can not be used for +longer counts; LFSR's are hard to invert (table lookup seems to be +only known method), therefore also impractical for wider counters. RLA +counter is still too slow and complex for wider counters and moderate +speeds (e.g. > 24bits @ >100MHz). + +As a consequence, the proposed counter uses synchronous divide-by-two +blocks, each using 1-bit pipeline and carry by single-clock +pulse. Design is simple and fast, preliminary results from Synplify +and Actel Designer shows 32bits @200MHz feasible. + +However, output bit lines are non-proportionaly delayed by discrete +number of clock periods. Therefore, to obtain linear bit word, an +inversion formula needs to be applied. Fortunately, the inversion is +simple (unlike LFSR's), in C (pcount.c): + + for (k = 1; k < n; k++) + if ((y & ((1< \ No newline at end of file Index: trunk/COPYING =================================================================== --- trunk/COPYING (nonexistent) +++ trunk/COPYING (revision 2) @@ -0,0 +1,165 @@ + GNU LESSER GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + + This version of the GNU Lesser General Public License incorporates +the terms and conditions of version 3 of the GNU General Public +License, supplemented by the additional permissions listed below. + + 0. Additional Definitions. + + As used herein, "this License" refers to version 3 of the GNU Lesser +General Public License, and the "GNU GPL" refers to version 3 of the GNU +General Public License. + + "The Library" refers to a covered work governed by this License, +other than an Application or a Combined Work as defined below. + + An "Application" is any work that makes use of an interface provided +by the Library, but which is not otherwise based on the Library. +Defining a subclass of a class defined by the Library is deemed a mode +of using an interface provided by the Library. + + A "Combined Work" is a work produced by combining or linking an +Application with the Library. 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Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. + + Each version is given a distinguishing version number. If the +Library as you received it specifies that a certain numbered version +of the GNU Lesser General Public License "or any later version" +applies to it, you have the option of following the terms and +conditions either of that published version or of any later version +published by the Free Software Foundation. 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Index: trunk/pdivtwo.vhdl =================================================================== --- trunk/pdivtwo.vhdl (nonexistent) +++ trunk/pdivtwo.vhdl (revision 2) @@ -0,0 +1,41 @@ +-- +-- * pipelined synchronous pulse counter * +-- pdivtwo -- core 1-stage element (pipelined f/2 divider) +-- +-- fast counter for slow-carry architectures +-- non-monotonic counting, value calculable by HDL/CPU +-- +-- idea&code by Marek Peca 08/2012 +-- Vyzkumny a zkusebni letecky ustav, a.s. http://vzlu.cz/ +-- thanks to Michael Vacek for testing +-- + +library ieee; +use ieee.std_logic_1164.all; +use ieee.numeric_std.all; + +entity pdivtwo is + port ( + clock: in std_logic; + en: in std_logic; + q, p: out std_logic + ); +end pdivtwo; + +architecture behavioral of pdivtwo is + signal state: std_logic := '1'; + signal pipe: std_logic := '0'; + signal next_state, next_pipe: std_logic; +begin + next_state <= not state when en = '1' else state; + next_pipe <= state and en; + p <= pipe; + q <= state; + + process + begin + wait until clock'event and clock = '1'; + state <= next_state; + pipe <= next_pipe; + end process; +end behavioral; Index: trunk/pcount.c =================================================================== --- trunk/pcount.c (nonexistent) +++ trunk/pcount.c (revision 2) @@ -0,0 +1,41 @@ +#include +#include +#include +#include + +typedef unsigned long count_t; + +count_t pcount_decode(unsigned n, count_t b) { + count_t y = b; + unsigned k; + for (k = 1; k < n; k++) + if ((y & ((1< 0; k--) + if ((b & ((1< %08lx -> %08lx\n", b, y, z); + } + return 0; +} Index: trunk/pcount_tb.vhdl =================================================================== --- trunk/pcount_tb.vhdl (nonexistent) +++ trunk/pcount_tb.vhdl (revision 2) @@ -0,0 +1,46 @@ +library ieee; +use ieee.std_logic_1164.all; +use ieee.numeric_std.all; +use std.textio.all; + +entity pcount_tb is +end pcount_tb; + +architecture test of pcount_tb is + component pdchain + generic ( + n: natural + ); + port ( + clock: in std_logic; + en: in std_logic; + q: out std_logic_vector (n-1 downto 0) + ); + end component; + -- + constant T: time := 5 ns; + signal clock: std_logic := '0'; + signal count: std_logic_vector (23 downto 0); +begin + pdchain0: pdchain + generic map ( + n => count'length + ) + port map ( + clock => clock, + en => '1', + q => count + ); + + clk: process + variable s: line; + begin + clock <= '1'; + wait for T/2; + clock <= '0'; + wait for T/2; + -- + write(s, to_bitvector(count)); + writeline(output, s); + end process; +end test; Index: trunk/Makefile =================================================================== --- trunk/Makefile (nonexistent) +++ trunk/Makefile (revision 2) @@ -0,0 +1,27 @@ +UNITS=pdchain.vhdl pdivtwo.vhdl +UNIT_TOP=pcount_tb.vhdl + +TOP_EXE=$(patsubst %.vhdl,%,$(UNIT_TOP)) +COPT=--ieee=synopsys -g +ROPT=--vcd=$(TOP_EXE).vcd --stop-time=10us + + +all: $(TOP_EXE) pcount + +testvcd: $(TOP_EXE) + ghdl -r $(TOP_EXE) $(ROPT) + +testrun: $(TOP_EXE) pcount + ghdl -r $(TOP_EXE) | ./pcount + +$(TOP_EXE): $(UNITS) $(UNIT_TOP) + ghdl -i $(UNITS) $(UNIT_TOP) + ghdl -a $(COPT) $(UNIT_TOP) + ghdl -m $(COPT) $(TOP_EXE) + +pcount: pcount.c + $(CC) -Wall -O -o $@ $< + +clean: + rm -rf $(TOP_EXE) pcount + ghdl --remove

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