EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 2

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1 EE108A Lecture 10: Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 1 Annuncement Prblem et 3 due Lab 4 hint D a gd clean deign Lab 5 and the final prject will reue mt f thi lab Yu ll regret any mitake here fr the ret f the quarter We ve detailed the interface t try and make thi eaier Undertand hw the lab wrk, nt jut hw t build it Hw ine wave are generated (handut) Hw t make FSM Timing Diagram t deal with memrie and data path (lat ectin f lab handut) Hw all the mdule interact (a gd blck diagram really help) Split up mdule deign and teting Decide n hw a mdule huld wrk a a grup Have ne pern deign it and the ther pern write the tet bench Find errr in deign and decriptin Watch yur timing Check yur ynthei reprt t make ure yu are meeting timing (If yur critical path i t lng yur deign invalid.) Run the timing analyzer and find the path that are t lw Find the path n yur blck diagram and figure ut where t inert pipeline regiter t plit up the lng path withut ling ynchrnizatin. (Hint: befre and after multiplier, but watch ut fr cntrl path!) EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 2 1

2 Micrcde an FSM realized with a memry array Original cncept by Wilke (1951) Put tate table in a memry (ROM r RAM) ROM Addre = {current tate, input} ROM Output = {next tate, utput} Effectively replace the cmbinatinal next tate lgic blck with the full truth table. Why i thi gd? Why might thi be bad? EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 3 Micrcde the picture Lk a lt like the cmbinatinal lgic blck frm regular FSM. next D Q tate +i a Memry d + input i n_ut D Q ut Memry ize: Ttal: 2 +i addree + bit per addre 2 +i *(+) bit clk EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 4 2

3 Example: Simple Light-Traffic Cntrller carew gn carew yn gew yew tate utput gyr gyr n ew EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 5 Re-writing State Table Of Example ROM Addre: {tate, input} ROM Output: {next tate, utput} State Next State Output State carew addre data!carew carew gn gn yn yn gew yew gew yew Nte: We ve enumerated every pible cmbinatin f input and tate. I thi efficient? EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 6 3

4 Micrcde Of Light-Traffic Cntrller carew 000: : : : : : : : next 2 n_ut 6 D D Q Q 2 6 tate light clk EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 7 Micrcded Traffic Light Cntrller in Verilg mdule ucdetlc(clk,rt,in,ut) ; parameter n = 1 ; // input width parameter m = 6 ; // utput width parameter k = 2 ; // bit f tate input clk, rt ; input [n-1:0] in ; utput [m-1:0] ut ; wire [k-1:0] next, tate ; wire [k+m-1:0] uint ; DFF #(k) tate_reg(clk, next, tate) ; // tate regiter DFF #(m) ut_reg(clk, uint[m-1:0], ut) ; // utput regiter ROM #(n+k,m+k) uc({tate, in}, uint) ; // micrcde tre aign next = rt? {k{1'b0}} : uint[m+k-1:m] ; // reet tate endmdule EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 8 4

5 Wavefrm Of Light-Traffic Cntrller Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 9 A New-and-Imprved Light-Traffic Cntrller Additinal functin t riginal Light-Traffic Cntrller: Light tay green in eat-wet directin a lng a car_ew i true. Light tay green in nrth-uth directin fr a minimum f 3 tate (GNS1, GNS2, and GNS3). After a yellw light, light huld g red in bth directin fr 1 cycle befre turning new light green. EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 10 5

6 Light-Traffic Cntrl State Diagram car_ew GNS1 GNS2 GNS3 car_ew YNS car_ew REW YEW car_ew GEW RNS EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 11 Light-Traffic Cntrller State Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 12 6

7 Wavefrm Of Light-Traffic Cntrller Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 13 Intructin Sequencing With lt f input, ize f memry increae rapidly (expnentially). Can reduce memry ize by berving: Mt f the time we mve t the next tate. We uually nly need t branch t ne ther tate baed ne (r a few) input. Add a micrprgram cunter (µpc) regiter t implify tate equencing. (Think f the PC a the current tate f the FSM.) Next tate i nw µpc+1 unle we are branching EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 14 7

8 Intructin Sequencing the picture branch_target Mux nextpc µpc 1 D Q a Memry d ++b 0 2 n_ut D Q 3 input i Branch Lgic clk ut branch_intructin b EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 15 Branching Lgic Branch lgic elect between µpc+1 and branch_target, depending n input and branch_intructin. Intructin are f the frm branch if f(input) Fr example branch if car_ew r branch if nt car_ew NOTE: The example ha changed here. Input are nw car Eat/Wet and Left Turn fr Nrth/Suth. Output are nw: NS{gyr}LT{gyr}EW{gyr} Lgic: tay green Eat/Wet until a Left Turn input cme in. EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 16 8

9 Branch Micrintructin Opcde NOP br brlt brnlt brew brnew Encding Decriptin N branch alway g t next intructin Alway branch Branch when left-turn car i detected Branch if n left-turn car i detected Branch when eat-wet car i detected Branch if n eat-wet car i detected EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 17 Micrcde Of Traffic-Light Cntrller With Branche State Addr Int Target Output ng brlt lt green n ng brnew ng green n ew np yellw n ew brew ew green ew ew br ng yellw ew lt np yellw n lt brlt lt green lt lt br ng yellw lt EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 18 9

10 Micrintructin Frmat br int br target utput b Fr ur example: b = 3 = 4 = 9 EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 19 Implementing Micrcde Of Light-Traffic Cntrller With Branche Uing Verilg mdule ucdeis(clk,rt,in,ut) ; parameter n = 2 ; // input width parameter m = 9 ; // utput width parameter k = 4 ; // bit f tate parameter j = 3 ; // bit f intructin input clk, rt ; input [n-1:0] in ; utput [m-1:0] ut ; wire [k-1:0] nupc, upc ; // micrprgram cunter wire [j+k+m-1:0] uint ; // micrintructin wrd // plit ff field f micrintructin wire [m-1:0] nxt_ut ; // = uint[m-1:0] ; wire [k-1:0] br_upc ; // = uint[m+k-1:m] ; wire [j-1:0] brint ; // = uint[m+j+k-1:m+k] ; aign {brint, br_upc, nxt_ut} = uint ; DFF #(k) upc_reg(clk, nupc, upc) ; // micrprgram cunter DFF #(m) ut_reg(clk, nxt_ut, ut) ; // utput regiter ROM #(k,m+k+j) uc(upc, uint) ; // micrcde tre // branch intructin decde wire branch = (brint[0] & in[0] brint[1] & in[1]) ^ brint[2] ; // equencer aign nupc = rt? {k{1'b0}} : branch? br_upc : upc + 1'b1 ; endmdule EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 20 10

11 Micrcde Of Light-Traffic Cntrller With Left Turn EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 21 Wavefrm Of Light-Traffic Cntrller With Left Turn Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 22 11

12 Alternate Micrcde Fr Light-Traffic Cntrller With Left Turn Previu micrcde ha: 2 tate with GNS light (NS1 & NS2) 2 tate with YNS light (EW1 & LT1) By adding a new branch intructin BNA: 1 tate with GNS light (NS1) 1 tate with YNS light (NS2) EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 23 Wavefrm Of Alternate Micrcde EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 24 12

13 Multiple Intructin Type Fr me FSM the micr-intructin wrd can tart getting a bit lng. T hrten it, we berve: Nt every tate need a branch Nt every utput change n every tate Define intructin that de jut a branch r a lad f ne regiter: brx 1yyyvvvv - branch t value vvvv n cnditin yyy ldx - 0yyyvvvv - lad regiter yyy with value vvvv Nte the tradeff: mre intructin (can nly branch r change utput n each intructin) but each intructin i much maller. EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 25 Intructin Frmat Of Micrcde With 2 Intructin Type Branch Intructin Stre Intructin 1 cnditin branch target 0 detinatin value Branch Intructin: Operate branch mux a befre N write t utput regiter Lad Intructin: Set branch mux t +1 Update elected utput regiter: Can include ther datapath cmpnent e.g., timer in place f an utput regiter EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 26 13

14 Blck Diagram Of Micrcde With Output Intructin Multiple utput regiter: E.g., NS/EW/LT target/value Mux nupc upc 1 D Q a Memry d x input i Branch Lgic intructin x x Output Decde n e1 en D Q E clk D Q E clk ut1 utn EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 27 Micrcde Fr Traffic-Light Cntrller With brx & ldx Intructin Regiter t lad: ldn lad nrth/uth light with value ldlt lad left-turn light with value ldew lad eat/wet light with value ltim1 lad timer 1 with value tart timer EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 28 14

15 Micrcde Fr Traffic-Light Cntrller With brx & ldx Intructin (Cnt) NS Green Until input NS Yellw t Red EW r LT? Wait fr NS Red, make EW Green State Addr Int Value rt ldlt RED rt ldew RED n ldn GREEN n ltim T_GREEN n bntz n4 n brnle n5 n ldn YELLOW n ltim T_YELLOW n bntz n8 n ldn RED n blt lt1 ew ltim T_RED ew bntz ew2 ew ldew GREEN ew ltim T_GREEN ew bntz ew5 ew ldew YELLOW EW t ew ltim T_YELLOW Red ew bntz ew8 ew ldew RED Back t NS ew br n1 Wait fr lt ltim T_RED NS Red, lt bntz lt2 make LT lt ldlt GREEN Green lt ltim T_GREEN lt bntz lt5 lt ldlt YELLOW LT t lt ltim T_YELLOW Red lt bntz lt8 lt ldlt RED Back t NS lt br n1 EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 29 Implementing Traffic-Light Cntrller Micrcde With brx & ldx Intructin In Verilg // mdule ucdemi(clk,rt,in,ut) ; parameter n = 2 ; // input width parameter m = 9 ; // utput width parameter = 3 ; // utput ub-width parameter k = 5 ; // bit f tate parameter j = 4 ; // bit f intructin input clk, rt ; input [n-1:0] in ; utput [m-1:0] ut ; wire [k-1:0] nupc, upc ; // micrprgram cunter wire [j+k-1:0] uint ; // micrintructin wrd wire dne ; // timer dne ignal // plit ff field f micrintructin wire pcde ; // pcde bit wire [j-2:0] int ; // cnditin fr branch, det fr tre wire [k-1:0] value ; // target fr branch, value fr tre aign {pcde, int, value} = uint ; T be cntinued n next page EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 30 15

16 Implementing Traffic-Light Cntrller Micrcde With brx & ldx Intructin In Verilg (Cnt) DFF #(k) upc_reg(clk, nupc, upc) ; // micrprgram cunter ROM #(k,k+j) uc(upc, uint) ; // micrcde tre // utput regiter and timer DFFE #() r0(clk, e[0], value[-1:0], ut[-1:0]) ; // NS DFFE #() r1(clk, e[1], value[-1:0], ut[2*-1:]) ; // EW DFFE #() r2(clk, e[2], value[-1:0], ut[3*-1:2*]) ; // LT Timer #(k) tim(clk, rt, e[3], value, dne) ; // timer // enable fr utput regiter and timer wire [3:0] e = pcde? 4'b0 : 1<<int ; // branch intructin decde wire branch = pcde? (int[2] ^ (((int[1:0] == 0) & in[0]) // BLT ((int[1:0] == 1) & in[1]) // BEW ((int[1:0] == 2) & (in[0] in[1])) //BLE ((int[1:0] == 3) & dne))) // BTD : 1'b0 ; // fr a tre pcde // micrprgram cunter aign nupc = rt? {k{1'b0}} : branch? value : upc + 1'b1 ; endmdule EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 31 Summary Micrcde i jut FSM implemented with a ROM r RAM One addre fr each tate x input cmbinatin Addre cntain next tate and utput Adding a equencer reduce ize f ROM/RAM One entry per tate rather than 2 input µpc, incrementer, branch addre, and branch cntrl Adding intructin type reduce width f ROM/RAM Branch r utput in each intructin rather than bth Type field pecifie which ne Need mre intructin, but each i maller One tep away frm a full prcer Jut add mre intructin (defer until EE108B) EE 108A Lecture 9 (c) 2006 W. J. Dally and D. Black-Schaffer 32 16