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[/] [eco32/] [trunk/] [fpga/] [mc/] [src/] [cpu/] [cpu_bus.v] - Blame information for rev 333

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//
// cpu_bus.v -- the ECO32 CPU bus interface
//
 
 
`timescale 1ns/10ps
`default_nettype none
 
 
module cpu_bus(clk, rst,
               bus_stb, bus_we, bus_addr,
               bus_din, bus_dout, bus_ack, bus_irq,
               cpu_stb, cpu_we, cpu_size, cpu_addr,
               cpu_din, cpu_dout, cpu_ack, cpu_irq);
    // bus interface
    input clk;
    input rst;
    output reg bus_stb;
    output reg bus_we;
    output reg [31:2] bus_addr;
    input [31:0] bus_din;
    output reg [31:0] bus_dout;
    input bus_ack;
    input [15:0] bus_irq;
    // CPU interface
    input cpu_stb;
    input cpu_we;
    input [1:0] cpu_size;
    input [31:0] cpu_addr;
    output reg [31:0] cpu_din;
    input [31:0] cpu_dout;
    output reg cpu_ack;
    output [15:0] cpu_irq;
 
  reg state;
  reg next_state;
  reg [31:0] wbuf;
  reg wbuf_we;
  reg [31:0] wbuf_in;
 
  // ctrl
  always @(posedge clk) begin
    if (rst) begin
      state <= 0;
    end else begin
      state <= next_state;
    end
  end
 
  // output
  always @(*) begin
    case (state)
      1'b0:
        if (~cpu_stb) begin
          // no bus activity from cpu
          bus_stb = 1'b0;
          bus_we = 1'bx;
          bus_addr[31:2] = 30'bx;
          bus_dout[31:0] = 32'bx;
          cpu_din[31:0] = 32'bx;
          cpu_ack = 1'b0;
          next_state = 1'b0;
          wbuf_we = 1'b0;
          wbuf_in[31:0] = 32'bx;
        end else begin
          // bus activated by cpu
          if (~cpu_we) begin
            // cpu read cycle
            if (~cpu_size[1]) begin
              if (~cpu_size[0]) begin
                // cpu read byte
                bus_stb = 1'b1;
                bus_we = 1'b0;
                bus_addr[31:2] = cpu_addr[31:2];
                bus_dout[31:0] = 32'bx;
                if (~cpu_addr[1]) begin
                  if (~cpu_addr[0]) begin
                    cpu_din[31:0] = { 24'h0, bus_din[31:24] };
                  end else begin
                    cpu_din[31:0] = { 24'h0, bus_din[23:16] };
                  end
                end else begin
                  if (~cpu_addr[0]) begin
                    cpu_din[31:0] = { 24'h0, bus_din[15: 8] };
                  end else begin
                    cpu_din[31:0] = { 24'h0, bus_din[ 7: 0] };
                  end
                end
                cpu_ack = bus_ack;
                next_state = 1'b0;
                wbuf_we = 1'b0;
                wbuf_in[31:0] = 32'bx;
              end else begin
                // cpu read halfword
                bus_stb = 1'b1;
                bus_we = 1'b0;
                bus_addr[31:2] = cpu_addr[31:2];
                bus_dout[31:0] = 32'bx;
                if (~cpu_addr[1]) begin
                  cpu_din[31:0] = { 16'h0, bus_din[31:16] };
                end else begin
                  cpu_din[31:0] = { 16'h0, bus_din[15: 0] };
                end
                cpu_ack = bus_ack;
                next_state = 1'b0;
                wbuf_we = 1'b0;
                wbuf_in[31:0] = 32'bx;
              end
            end else begin
              // cpu read word
              bus_stb = 1'b1;
              bus_we = 1'b0;
              bus_addr[31:2] = cpu_addr[31:2];
              bus_dout[31:0] = 32'bx;
              cpu_din[31:0] = bus_din[31:0];
              cpu_ack = bus_ack;
              next_state = 1'b0;
              wbuf_we = 1'b0;
              wbuf_in[31:0] = 32'bx;
            end
          end else begin
            // cpu write cycle
            if (~cpu_size[1]) begin
              if (~cpu_size[0]) begin
                // cpu write byte
                // part 1: read word into word buffer
                bus_stb = 1'b1;
                bus_we = 1'b0;
                bus_addr[31:2] = cpu_addr[31:2];
                bus_dout[31:0] = 32'bx;
                cpu_din[31:0] = 32'bx;
                cpu_ack = 1'b0;
                if (~bus_ack) begin
                  next_state = 1'b0;
                end else begin
                  next_state = 1'b1;
                end
                wbuf_we = 1'b1;
                if (~cpu_addr[1]) begin
                  if (~cpu_addr[0]) begin
                    wbuf_in[31:0] = { cpu_dout[7:0], bus_din[23:16],
                                      bus_din[15:8], bus_din[7:0] };
                  end else begin
                    wbuf_in[31:0] = { bus_din[31:24], cpu_dout[7:0],
                                      bus_din[15:8], bus_din[7:0] };
                  end
                end else begin
                  if (~cpu_addr[0]) begin
                    wbuf_in[31:0] = { bus_din[31:24], bus_din[23:16],
                                      cpu_dout[7:0], bus_din[7:0] };
                  end else begin
                    wbuf_in[31:0] = { bus_din[31:24], bus_din[23:16],
                                      bus_din[15:8], cpu_dout[7:0] };
                  end
                end
              end else begin
                // cpu write halfword
                // part 1: read word into word buffer
                bus_stb = 1'b1;
                bus_we = 1'b0;
                bus_addr[31:2] = cpu_addr[31:2];
                bus_dout[31:0] = 32'bx;
                cpu_din[31:0] = 32'bx;
                cpu_ack = 1'b0;
                if (~bus_ack) begin
                  next_state = 1'b0;
                end else begin
                  next_state = 1'b1;
                end
                wbuf_we = 1'b1;
                if (~cpu_addr[1]) begin
                  wbuf_in[31:0] = { cpu_dout[15:0], bus_din[15:0] };
                end else begin
                  wbuf_in[31:0] = { bus_din[31:16], cpu_dout[15:0] };
                end
              end
            end else begin
              // cpu write word
              bus_stb = 1'b1;
              bus_we = 1'b1;
              bus_addr[31:2] = cpu_addr[31:2];
              bus_dout[31:0] = cpu_dout[31:0];
              cpu_din[31:0] = 32'bx;
              cpu_ack = bus_ack;
              next_state = 1'b0;
              wbuf_we = 1'b0;
              wbuf_in[31:0] = 32'bx;
            end
          end
        end
      1'b1:
        begin
          // cpu write halfword or byte
          // part 2: write word from word buffer
          bus_stb = 1'b1;
          bus_we = 1'b1;
          bus_addr[31:2] = cpu_addr[31:2];
          bus_dout[31:0] = wbuf[31:0];
          cpu_din[31:0] = 32'bx;
          cpu_ack = bus_ack;
          if (~bus_ack) begin
            next_state = 1'b1;
          end else begin
            next_state = 1'b0;
          end
          wbuf_we = 1'b0;
          wbuf_in[31:0] = 32'bx;
        end
    endcase
  end
 
  // word buffer
  always @(posedge clk) begin
    if (wbuf_we) begin
      wbuf[31:0] <= wbuf_in[31:0];
    end
  end
 
  // interrupt requests
  assign cpu_irq[15:0] = bus_irq[15:0];
 
endmodule

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[/] [eco32/] [trunk/] [fpga/] [mc/] [src/] [cpu/] [cpu_bus.v] - Blame information for rev 333

Line No.	Rev	Author	Line
1	290	hellwig	`//`
2			`// cpu_bus.v -- the ECO32 CPU bus interface`
3			`//`
4
5
6			`timescale 1ns/10ps
7			`default_nettype none
8
9
10			`module cpu_bus(clk, rst,`
11			`bus_stb, bus_we, bus_addr,`
12			`bus_din, bus_dout, bus_ack, bus_irq,`
13			`cpu_stb, cpu_we, cpu_size, cpu_addr,`
14			`cpu_din, cpu_dout, cpu_ack, cpu_irq);`
15			`// bus interface`
16			`input clk;`
17			`input rst;`
18			`output reg bus_stb;`
19			`output reg bus_we;`
20			`output reg [31:2] bus_addr;`
21			`input [31:0] bus_din;`
22			`output reg [31:0] bus_dout;`
23			`input bus_ack;`
24			`input [15:0] bus_irq;`
25			`// CPU interface`
26			`input cpu_stb;`
27			`input cpu_we;`
28			`input [1:0] cpu_size;`
29			`input [31:0] cpu_addr;`
30			`output reg [31:0] cpu_din;`
31			`input [31:0] cpu_dout;`
32			`output reg cpu_ack;`
33			`output [15:0] cpu_irq;`
34
35			`reg state;`
36			`reg next_state;`
37			`reg [31:0] wbuf;`
38			`reg wbuf_we;`
39			`reg [31:0] wbuf_in;`
40
41			`// ctrl`
42			`always @(posedge clk) begin`
43			`if (rst) begin`
44			`state <= 0;`
45			`end else begin`
46			`state <= next_state;`
47			`end`
48			`end`
49
50			`// output`
51			`always @(*) begin`
52			`case (state)`
53			`1'b0:`
54			`if (~cpu_stb) begin`
55			`// no bus activity from cpu`
56			`bus_stb = 1'b0;`
57			`bus_we = 1'bx;`
58			`bus_addr[31:2] = 30'bx;`
59			`bus_dout[31:0] = 32'bx;`
60			`cpu_din[31:0] = 32'bx;`
61			`cpu_ack = 1'b0;`
62			`next_state = 1'b0;`
63			`wbuf_we = 1'b0;`
64			`wbuf_in[31:0] = 32'bx;`
65			`end else begin`
66			`// bus activated by cpu`
67			`if (~cpu_we) begin`
68			`// cpu read cycle`
69			`if (~cpu_size[1]) begin`
70			`if (~cpu_size[0]) begin`
71			`// cpu read byte`
72			`bus_stb = 1'b1;`
73			`bus_we = 1'b0;`
74			`bus_addr[31:2] = cpu_addr[31:2];`
75			`bus_dout[31:0] = 32'bx;`
76			`if (~cpu_addr[1]) begin`
77			`if (~cpu_addr[0]) begin`
78			`cpu_din[31:0] = { 24'h0, bus_din[31:24] };`
79			`end else begin`
80			`cpu_din[31:0] = { 24'h0, bus_din[23:16] };`
81			`end`
82			`end else begin`
83			`if (~cpu_addr[0]) begin`
84			`cpu_din[31:0] = { 24'h0, bus_din[15: 8] };`
85			`end else begin`
86			`cpu_din[31:0] = { 24'h0, bus_din[ 7: 0] };`
87			`end`
88			`end`
89			`cpu_ack = bus_ack;`
90			`next_state = 1'b0;`
91			`wbuf_we = 1'b0;`
92			`wbuf_in[31:0] = 32'bx;`
93			`end else begin`
94			`// cpu read halfword`
95			`bus_stb = 1'b1;`
96			`bus_we = 1'b0;`
97			`bus_addr[31:2] = cpu_addr[31:2];`
98			`bus_dout[31:0] = 32'bx;`
99			`if (~cpu_addr[1]) begin`
100			`cpu_din[31:0] = { 16'h0, bus_din[31:16] };`
101			`end else begin`
102			`cpu_din[31:0] = { 16'h0, bus_din[15: 0] };`
103			`end`
104			`cpu_ack = bus_ack;`
105			`next_state = 1'b0;`
106			`wbuf_we = 1'b0;`
107			`wbuf_in[31:0] = 32'bx;`
108			`end`
109			`end else begin`
110			`// cpu read word`
111			`bus_stb = 1'b1;`
112			`bus_we = 1'b0;`
113			`bus_addr[31:2] = cpu_addr[31:2];`
114			`bus_dout[31:0] = 32'bx;`
115			`cpu_din[31:0] = bus_din[31:0];`
116			`cpu_ack = bus_ack;`
117			`next_state = 1'b0;`
118			`wbuf_we = 1'b0;`
119			`wbuf_in[31:0] = 32'bx;`
120			`end`
121			`end else begin`
122			`// cpu write cycle`
123			`if (~cpu_size[1]) begin`
124			`if (~cpu_size[0]) begin`
125			`// cpu write byte`
126			`// part 1: read word into word buffer`
127			`bus_stb = 1'b1;`
128			`bus_we = 1'b0;`
129			`bus_addr[31:2] = cpu_addr[31:2];`
130			`bus_dout[31:0] = 32'bx;`
131			`cpu_din[31:0] = 32'bx;`
132			`cpu_ack = 1'b0;`
133			`if (~bus_ack) begin`
134			`next_state = 1'b0;`
135			`end else begin`
136			`next_state = 1'b1;`
137			`end`
138			`wbuf_we = 1'b1;`
139			`if (~cpu_addr[1]) begin`
140			`if (~cpu_addr[0]) begin`
141			`wbuf_in[31:0] = { cpu_dout[7:0], bus_din[23:16],`
142			`bus_din[15:8], bus_din[7:0] };`
143			`end else begin`
144			`wbuf_in[31:0] = { bus_din[31:24], cpu_dout[7:0],`
145			`bus_din[15:8], bus_din[7:0] };`
146			`end`
147			`end else begin`
148			`if (~cpu_addr[0]) begin`
149			`wbuf_in[31:0] = { bus_din[31:24], bus_din[23:16],`
150			`cpu_dout[7:0], bus_din[7:0] };`
151			`end else begin`
152			`wbuf_in[31:0] = { bus_din[31:24], bus_din[23:16],`
153			`bus_din[15:8], cpu_dout[7:0] };`
154			`end`
155			`end`
156			`end else begin`
157			`// cpu write halfword`
158			`// part 1: read word into word buffer`
159			`bus_stb = 1'b1;`
160			`bus_we = 1'b0;`
161			`bus_addr[31:2] = cpu_addr[31:2];`
162			`bus_dout[31:0] = 32'bx;`
163			`cpu_din[31:0] = 32'bx;`
164			`cpu_ack = 1'b0;`
165			`if (~bus_ack) begin`
166			`next_state = 1'b0;`
167			`end else begin`
168			`next_state = 1'b1;`
169			`end`
170			`wbuf_we = 1'b1;`
171			`if (~cpu_addr[1]) begin`
172			`wbuf_in[31:0] = { cpu_dout[15:0], bus_din[15:0] };`
173			`end else begin`
174			`wbuf_in[31:0] = { bus_din[31:16], cpu_dout[15:0] };`
175			`end`
176			`end`
177			`end else begin`
178			`// cpu write word`
179			`bus_stb = 1'b1;`
180			`bus_we = 1'b1;`
181			`bus_addr[31:2] = cpu_addr[31:2];`
182			`bus_dout[31:0] = cpu_dout[31:0];`
183			`cpu_din[31:0] = 32'bx;`
184			`cpu_ack = bus_ack;`
185			`next_state = 1'b0;`
186			`wbuf_we = 1'b0;`
187			`wbuf_in[31:0] = 32'bx;`
188			`end`
189			`end`
190			`end`
191			`1'b1:`
192			`begin`
193			`// cpu write halfword or byte`
194			`// part 2: write word from word buffer`
195			`bus_stb = 1'b1;`
196			`bus_we = 1'b1;`
197			`bus_addr[31:2] = cpu_addr[31:2];`
198			`bus_dout[31:0] = wbuf[31:0];`
199			`cpu_din[31:0] = 32'bx;`
200			`cpu_ack = bus_ack;`
201			`if (~bus_ack) begin`
202			`next_state = 1'b1;`
203			`end else begin`
204			`next_state = 1'b0;`
205			`end`
206			`wbuf_we = 1'b0;`
207			`wbuf_in[31:0] = 32'bx;`
208			`end`
209			`endcase`
210			`end`
211
212			`// word buffer`
213			`always @(posedge clk) begin`
214			`if (wbuf_we) begin`
215			`wbuf[31:0] <= wbuf_in[31:0];`
216			`end`
217			`end`
218
219			`// interrupt requests`
220			`assign cpu_irq[15:0] = bus_irq[15:0];`
221
222			`endmodule`