One clock is enough

diff --git a/eval.v b/eval.v
index 8aa21590ca0ea88af0f0667a3b4db5b14f1dcddc..75a979c6a89691932a23d36f1dbda0d99adb27bf 100644 (file)
--- a/eval.v
+++ b/eval.v
@@ -1,11 +1,13 @@
-module EVAL(input clk, input mclk, input [15:0] Ein, output [15:0] Eout, output [3:0] gcop, output [5:0] ostate, input conn_ea, input conn_et);
+module EVAL(input clk, input clk_enable, input [15:0] Ein, output [15:0] Eout, output [3:0] gcop, output [5:0] ostate, input conn_ea, input conn_et);
    reg [21:0] rom_output;
    reg [5:0]  eostate = 6'o0;
    reg [5:0]  enstate;
    reg [15:0]  Ein_latched;
 
    always @(posedge clk) begin
-         Ein_latched <= Ein;
+         if(clk_enable) begin
+                Ein_latched <= Ein;
+         end
    end
 
    wire et_lit = rom_output[21];
@@ -94,10 +96,12 @@ module EVAL(input clk, input mclk, input [15:0] Ein, output [15:0] Eout, output
    end // always @ *
 
    always @ (posedge clk) begin
-         eostate <=
-                               et_disp ? (enstate | E[15:13]) :
-                               eaz_etz_eqv_disp ? (enstate | {ea_zero, et_zero, 1'b0}) :
-                               enstate;
+         if (clk_enable) begin
+                eostate <=
+                                  et_disp ? (enstate | E[15:13]) :
+                                  eaz_etz_eqv_disp ? (enstate | {ea_zero, et_zero, 1'b0}) :
+                                  enstate;
+         end
    end
 
    assign ostate = eostate;
@@ -127,10 +131,12 @@ module EVAL(input clk, input mclk, input [15:0] Ein, output [15:0] Eout, output
    assign Eout = EfromV | EfromX | EfromXp | EfromN | EfromL | EfromC | EfromLIT;
 
    always @ (posedge clk) begin
-         if (ldV) V <= E;
-         if (ldX) X <= E;
-         if (ldN) N <= E;
-         if (ldL) L <= E;
-         if (ldC) C <= E;
+         if (clk_enable) begin
+                if (ldV) V <= E;
+                if (ldX) X <= E;
+                if (ldN) N <= E;
+                if (ldL) L <= E;
+                if (ldC) C <= E;
+         end
    end
 endmodule // EVAL

diff --git a/gc.v b/gc.v
index d4521783c163d4a006c23b9e40ddecaf692cbf68..2bbada4f0aeac15103c0643e91274aa3feb550d9 100644 (file)
--- a/gc.v
+++ b/gc.v
@@ -1,13 +1,15 @@
 `include "gcram.v"
 
-module GC (input clk, input mclk, input [15:0] Ein, output [15:0] Eout, input [3:0] gcop, output [5:0] ostate, output conn_et, output conn_ea, output step_eval, output ram_we, output [12:0] ram_addr, output [15:0] ram_di, input [15:0] ram_do);
+module GC (input clk, input clk_enable, input [15:0] Ein, output [15:0] Eout, input [3:0] gcop, output [5:0] ostate, output conn_et, output conn_ea, output step_eval, output ram_we, output [12:0] ram_addr, output [15:0] ram_di, input [15:0] ram_do);
    reg [15:0] rom_output;
    reg [5:0]  gostate = 6'o0;
    reg [5:0]  gnstate;
    reg [15:0] Ein_latched = 16'b0100000000000100; // initial value of E
 
    always @(posedge clk) begin
-         Ein_latched <= Ein;
+         if(clk_enable) begin
+               Ein_latched <= Ein;
+         end
    end
 
    wire ga_zero_disp = rom_output[15];
@@ -84,10 +86,12 @@ module GC (input clk, input mclk, input [15:0] Ein, output [15:0] Eout, input [3
    end // always @ *
 
    always @ (posedge clk) begin
-         gostate <=
-                               ga_zero_disp ? (gnstate | ga_zero) :
-                               gcop_disp ? (gnstate | gcop) :
-                               gnstate;
+         if(clk_enable) begin
+                gostate <=
+                                  ga_zero_disp ? (gnstate | ga_zero) :
+                                  gcop_disp ? (gnstate | gcop) :
+                                  gnstate;
+         end
    end // always @ (posedge clk)
 
    assign ostate = gostate;
@@ -121,10 +125,12 @@ module GC (input clk, input mclk, input [15:0] Ein, output [15:0] Eout, input [3
    assign Eout[15:13] = conn_et ? Gout[15:13] : 0;
 
    always @ (posedge clk) begin
-         if (ldS) S = G;
-         if (ldP) P <= G[12:0];
-         if (ldR) R <= G;
-         if (ldQ) Q <= G;
-         if (adr) A <= S[12:0];
+         if(clk_enable) begin
+                if (ldS) S = G;
+                if (ldP) P <= G[12:0];
+                if (ldR) R <= G;
+                if (ldQ) Q <= G;
+                if (adr) A <= S[12:0];
+         end
    end
 endmodule // GC

diff --git a/lisp_processor.v b/lisp_processor.v
index 7be974bcb1bc99c85ff76b277fee60cfbe12cdba..2ae446f753538e951589853f90e26fd9fbbf08be 100644 (file)
--- a/lisp_processor.v
+++ b/lisp_processor.v
@@ -34,8 +34,8 @@ module PROCESSOR (input clk, output [4:0] led, output uart_tx, input uart_rx);
 
    reg [1:0]  counter = 0;
 
-   wire gc_clock = counter[1] & !initial_reset;
-   wire eval_clock = !counter[1] & step_eval & !initial_reset;
+   wire gc_clock_enable   = counter[0] &  counter[1] & !initial_reset;
+   wire eval_clock_enable = counter[0] & !counter[1] & step_eval & !initial_reset;
 
    always @ (posedge clk)
         counter <= counter + 1;
@@ -57,9 +57,9 @@ module PROCESSOR (input clk, output [4:0] led, output uart_tx, input uart_rx);
 
    GCRAM gcram (.clk(clk), .we(ram_we), .addr(ram_addr), .di(ram_di), .do(ram_do), .result(result));
 
-   GC gc (.clk(gc_clock), .mclk(clk), .Ein(E1), .Eout(E2), .gcop(gcop), .ostate(gostate), .step_eval(step_eval), .conn_ea(conn_ea), .conn_et(conn_et), .ram_we(ram_we), .ram_addr(ram_addr), .ram_di(ram_di), .ram_do(ram_do));
+   GC gc (.clk(clk), .clk_enable(gc_clock_enable), .Ein(E1), .Eout(E2), .gcop(gcop), .ostate(gostate), .step_eval(step_eval), .conn_ea(conn_ea), .conn_et(conn_et), .ram_we(ram_we), .ram_addr(ram_addr), .ram_di(ram_di), .ram_do(ram_do));
 
-   EVAL eval (.clk(eval_clock), .mclk(clk), .Ein(E2), .Eout(E1), .gcop(gcop), .ostate(eostate), .conn_ea(conn_ea), .conn_et(conn_et));
+   EVAL eval (.clk(clk), .clk_enable(eval_clock_enable), .Ein(E2), .Eout(E1), .gcop(gcop), .ostate(eostate), .conn_ea(conn_ea), .conn_et(conn_et));
 
    // UART outputs
    wire       uart_rx_signal;