L19 – Register Set

Dual Ported Register Set Design of a dual ported register set Ref: text Unit 10, 17, 20 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The objective Dual ported register set 2 data busses Can load or drive either bus No timing – only control To insure this unit will synthesize need to do it subcomponent by subcomponent and structurally. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Why dual ported? Traditional processor architecture Accumulator based operation RISC Reduced Instruction Set Computer Basis – all operations take 1 cycle Can’t achieve with an accumulator architecture Have to fetch 2nd argument 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU RISC Requirements Need to fetch both operands at once in one cycle Dedicated instructions Load Store Functional 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The bus drivers The code LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY busdr8 IS PORT (drive : IN std_logic; data : IN std_logic_vector(7 downto 0); intbus : OUT std_logic_vector(7 downto 0)); END busdr8; ARCHITECTURE one OF busdr8 IS BEGIN PROCESS (drive,data) IF (drive='1') THEN intbus <= data; ELSE intbus <= "ZZZZZZZZ"; END IF; END PROCESS; END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Quartis result The synthesis result Resources – tri-state pins 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU An 8 bit register This is code for an 8-bit register – 8 F/Fs LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY reg8 IS PORT (datain : IN std_logic_vector(7 downto 0); load : IN std_logic; dataout : OUT std_logic_vector(7 downto 0)); END reg8; ARCHITECTURE one OF reg8 IS BEGIN PROCESS (datain,load) IF (load='1' AND load'event) THEN dataout <= datain; END IF; END PROCESS; END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Synthesis results Results in just registers Resources – 8 registers on FPGA 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU 2-to-1 multiplexer 8-bit The code LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY mux2to1x8 IS PORT (linput,rinput : IN std_logic_vector(7 downto 0); sel : IN std_logic; dataout : OUT std_logic_vector(7 downto 0)); END mux2to1x8; ARCHITECTURE one OF mux2to1x8 IS BEGIN dataout <= linput when sel='0' ELSE rinput; END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Synthesis Results for mux 8-bit 2-to-1 mulitplexer Resources – 8 combinational LUTs 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Register line structure Diagram 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU A register line Combine the register, the bus drivers (one for ABUS, one for Bbus), and a 2-to-1 mux for selecting which bus to have for input. LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY reg_line_str IS PORT (ABUS,BBUS : INOUT std_logic_vector (7 downto 0); aload,bload : IN std_logic; adrive,bdrive : IN std_logic; sel : IN std_logic); END reg_line_str; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The code ARCHITECTURE one OF reg_line_str IS COMPONENT reg8 IS PORT (datain : IN std_logic_vector(7 downto 0); load : IN std_logic; dataout : OUT std_logic_vector(7 downto 0)); END COMPONENT; FOR all : reg8 USE ENTITY work.reg8(one); COMPONENT busdr8 IS PORT (drive : IN std_logic; data : IN std_logic_vector(7 downto 0); intbus : OUT std_logic_vector(7 downto 0)); FOR all : busdr8 USE ENTITY work.busdr8(one); COMPONENT mux2to1x8 IS PORT (linput,rinput : IN std_logic_vector(7 downto 0); sel : IN std_logic; FOR all : mux2to1x8 USE ENTITY work.mux2to1x8(one); -- INTERNAL SIGNALS SIGNAL muxout,regout : std_logic_vector (7 downto 0); SIGNAL muxsel,rload : std_logic; BEGIN m1 : mux2to1x8 PORT MAP (ABUS,BBUS,muxsel,muxout); muxsel <= Aload AND sel; r1 : reg8 PORT MAP (muxout,rload,regout); rload <= (Aload OR Bload) AND sel; abd : busdr8 PORT MAP (adrive,regout,ABUS); bbd : busdr8 PORT MAP (bdrive,regout,BBUS); END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The results Synthesis results for a single dual ported register. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Decoder to build a register set Need to activate the correct register from a register set. LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY decoder2to4 IS PORT (addr : IN std_logic_vector(1 downto 0); sel_line : OUT std_logic_vector(3 downto 0)); END decoder2to4; ARCHITECTURE one OF decoder2to4 IS BEGIN sel_line(0) <= NOT addr(1) AND NOT addr(0); sel_line(1) <= NOT addr(1) AND addr(0); sel_line(2) <= addr(1) AND NOT addr(0); sel_line(3) <= addr(1) AND addr(0); END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Decoder synthesis Synthesis gives Resources – pins and 4 combinaltional LUTs 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU A full register set A full register set would have at lease 8 registers. Here will start with 2 registers. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The code Have all the reference unit code. The first time abbreviated ENTITY interface – only the busses. LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY reg_set_2 IS PORT (ABUS,BBUS : INOUT std_logic_vector(7 downto 0)); END reg_set_2; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

The 2 register architecture ARCHITECTURE one OF reg_set_2 IS -- this architecture is to confirm the build up of bus units COMPONENT reg_line_str IS PORT (ABUS,BBUS : INOUT std_logic_vector (7 downto 0); aload,bload : IN std_logic; adrive,bdrive : IN std_logic; sel : IN std_logic); END COMPONENT; FOR all : reg_line_str USE ENTITY work.reg_line_str(one); -- now delcare signals for test setup SIGNAL aload1,bload1,adrive1,bdrive1,sel1 : std_logic; SIGNAL aload2,bload2,adrive2,bdrive2,sel2 : std_logic; BEGIN r1 : reg_line_str PORT MAP (ABUS,BBUS,aload1,bload1,adrive1,bdrive1,sel1); r2 : reg_line_str PORT MAP (ABUS,BBUS,aload2,bload2,adrive2,bdrive2,sel2); END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Quartis results After synthesis Report usage only shows pins – you have to traverse into each unit to get resources. Can see these by running cursor over the unit in the RTL viewer. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Usage summary by using cursor For each register line 32 buffers (regular) 2 combination ANDs 1 combination OR 8 DFF 16 Tri-state buffers 8 muxes 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Expanding register line unit Pushing down by double clicking in unit box The same unit from before 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Now moving control signals Move the control signals to the ENTITY. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The last step Adding a decoder to generate the selects This time a 1-to-2 decoder Then a bunch of errors popped up so back up. Do the implementation one step at a time Add the regno signal to the ENTITY WORKED FINE  Add the decoder COMPONENT – re-synthesize Add and instantiation for the decoder Finally link the decoder output to the select lines with concurrent signal assignment statements. It then started generating errors so starting a new approach. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The new approach Have a bus driver that works!!  LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY busdr8 IS PORT (drive : IN std_logic; data : IN std_logic_vector(7 downto 0); intbus : OUT std_logic_vector(7 downto 0)); END busdr8; ARCHITECTURE one OF busdr8 IS BEGIN PROCESS (drive,data) IF (drive='1') THEN intbus <= data; ELSE intbus <= "ZZZZZZZZ"; END IF; END PROCESS; END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Put together for four of them LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.all; ENTITY m4drv IS PORT (intbus : INOUT std_logic_vector(7 downto 0); data1,data2,data3,data4 : IN std_logic_vector(7 downto 0); dr1,dr2,dr3,dr4 : IN std_logic); END m4drv; ARCHITECTURE one OF m4drv IS COMPONENT busdr8 IS PORT (drive : IN std_logic; data : IN std_logic_vector(7 downto 0); intbus : OUT std_logic_vector(7 downto 0)); END COMPONENT; FOR all : busdr8 USE ENTITY work.busdr8(one); --internal signals BEGIN u1 : busdr8 PORT MAP (dr1,data1,intbus); u2 : busdr8 PORT MAP (dr2,data2,intbus); u3 : busdr8 PORT MAP (dr3,data3,intbus); u4 : busdr8 PORT MAP (dr4,data4,intbus); END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Results for bus driver Now have no fixed 0’s 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Prior results The prior results, although they looked like they worked, didn’t. ARCHITECTURE one OF mdrv IS COMPONENT busdr IS PORT (drive : IN std_logic; data : IN std_logic; intbus : OUT std_logic); END COMPONENT; FOR all : busdr USE ENTITY work.busdr(one); --internal signals SIGNAL dr1,dr2,dr3 : std_logic; SIGNAL data1,data2,data3 : std_logic; BEGIN u1 : busdr PORT MAP (dr1,data1,intbus); u2 : busdr PORT MAP (dr2,data2,intbus); u3 : busdr PORT MAP (dr3,data3,intbus); END one; 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Build up from drivers The architecture – Diagram not complete 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU The units The tri-state bus drivers 4 of them 8-bits each in a hierarchical unit The registers 4 of them as instantiated units Mux2to1x8 – a byte width 2 to 1 multiplexer used to select which input to have available to load into register, the ABUS or the BBUS Decoders 2 to 4 – takes the 2 bit register number and generates the correct select line – used for selecting which register to load from the ABUS or BBUS and which register to drive. Note that the system can drive just register. It is capable of two operations each cycle. Glue logic – generated the load and drive signals. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Results for the design Resources Pins – 24 ABUS – 8 BBUS – 8 aload,bload,adrive,bdrive – 4 aregno,bregno – 2 each – 4 Registers – 32 (4 registers 8-bits each) Combinational LUTs – 60 Average fanout – 3.31 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Synthesis results Quartis produced graphic 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Pushing down Decoder register and mux 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Next step The next step is the VHDL simulation of the register set to be sure its behavior is as desired. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU

Copyright 2012 - Joanne DeGroat, ECE, OSU Lecture summary Have seen how to create a 4 register location register-set. The next assignment is to use the code here (which is also on the web page) to generate a 8 location register. Simply build upon this code. 9/2/2012 – ECE 3561 Lect 9 Copyright 2012 - Joanne DeGroat, ECE, OSU