system: Remember to wire the DCache to the memory!
[firearm.git] / Memory.v
1 `include "ARM_Constants.v"
2
3 module Memory(
4         input clk,
5         input Nrst,
6
7         /* bus interface */
8         output reg [31:0] busaddr,
9         output reg rd_req,
10         output reg wr_req,
11         input rw_wait,
12         output reg [31:0] wr_data,
13         input [31:0] rd_data,
14
15         /* regfile interface */
16         output reg [3:0] st_read,
17         input [31:0] st_data,
18         
19         /* stage inputs */
20         input inbubble,
21         input [31:0] pc,
22         input [31:0] insn,
23         input [31:0] op0,
24         input [31:0] op1,
25         input [31:0] op2,
26         input write_reg,
27         input [3:0] write_num,
28         input [31:0] write_data,
29
30         /* outputs */
31         output reg outstall,
32         output reg outbubble,
33         output reg [31:0] outpc,
34         output reg [31:0] outinsn,
35         output reg out_write_reg = 1'b0,
36         output reg [3:0] out_write_num = 4'bxxxx,
37         output reg [31:0] out_write_data = 32'hxxxxxxxx
38         );
39
40         reg [31:0] addr, raddr;
41         reg next_notdone, next_inc_next;
42         reg [31:0] align_s1, align_s2, align_rddata;
43
44         wire next_outbubble;    
45         wire next_write_reg;
46         wire [3:0] next_write_num;
47         wire [31:0] next_write_data;
48
49         reg [15:0] regs, next_regs;
50
51         reg notdone = 1'b0;
52         reg inc_next = 1'b0;
53
54         always @(posedge clk)
55         begin
56                 outpc <= pc;
57                 outinsn <= insn;
58                 outbubble <= next_outbubble;
59                 out_write_reg <= next_write_reg;
60                 out_write_num <= next_write_num;
61                 out_write_data <= next_write_data;
62                 notdone <= next_notdone;
63                 inc_next <= next_inc_next;
64                 regs <= next_regs;
65         end
66
67         always @(*)
68         begin
69                 addr = 32'hxxxxxxxx;
70                 raddr = 32'hxxxxxxxx;
71                 rd_req = 1'b0;
72                 wr_req = 1'b0;
73                 wr_data = 32'hxxxxxxxx;
74                 busaddr = 32'hxxxxxxxx;
75                 outstall = 1'b0;
76                 next_notdone = 1'b0;
77                 next_write_reg = write_reg;
78                 next_write_num = write_num;
79                 next_write_data = write_data;
80                 next_inc_next = 1'b0;
81                 next_outbubble = inbubble;
82                 outstall = 1'b0;
83                 
84                 casez(insn)
85                 `DECODE_LDRSTR_UNDEFINED: begin end
86                 `DECODE_LDRSTR: begin
87                         if (!inbubble) begin
88                                 next_outbubble = rw_wait;
89                                 outstall = rw_wait | notdone;
90                         
91                                 addr = insn[23] ? op0 + op1 : op0 - op1; /* up/down select */
92                                 raddr = insn[24] ? op0 : addr; /* pre/post increment */
93                                 busaddr = {raddr[31:2], 2'b0};
94                                 rd_req = insn[20];
95                                 wr_req = ~insn[20];
96                                 
97                                 /* rotate to correct position */
98                                 align_s1 = raddr[1] ? {rd_data[15:0], rd_data[31:16]} : rd_data;
99                                 align_s2 = raddr[0] ? {align_s1[7:0], align_s1[31:8]} : align_s1;
100                                 /* select byte or word */
101                                 align_rddata = insn[22] ? {24'b0, align_s2[7:0]} : align_s2;
102                                 
103                                 if(!insn[20]) begin
104                                         wr_data = insn[22] ? {4{op2[7:0]}} : op2; /* XXX need to actually store just a byte */
105                                 end
106                                 else if(!inc_next) begin
107                                         next_write_reg = 1'b1;
108                                         next_write_num = insn[15:12];
109                                         next_write_data = align_rddata;
110                                         next_inc_next = 1'b1;
111                                 end
112                                 else if(insn[21]) begin
113                                         next_write_reg = 1'b1;
114                                         next_write_num = insn[19:16];
115                                         next_write_data = addr;
116                                 end
117                                 next_notdone = rw_wait & insn[20] & insn[21];
118                         end
119                 end
120                 `DECODE_LDMSTM: begin
121                         busaddr = {op0[31:2], 2'b0};
122                         rd_req = insn[20];
123                         wr_req = ~insn[20];
124                         casez(regs)
125                         16'b???????????????1: begin
126                                 next_regs = regs;
127                         end
128                         16'b??????????????10: begin
129                         end
130                         16'b?????????????100: begin
131                         end
132                         16'b????????????1000: begin
133                         end
134                         16'b???????????10000: begin
135                         end
136                         16'b??????????100000: begin
137                         end
138                         16'b?????????1000000: begin
139                         end
140                         16'b????????10000000: begin
141                         end
142                         16'b???????100000000: begin
143                         end
144                         16'b??????1000000000: begin
145                         end
146                         16'b?????10000000000: begin
147                         end
148                         16'b????100000000000: begin
149                         end
150                         16'b???1000000000000: begin
151                         end
152                         16'b??10000000000000: begin
153                         end
154                         16'b?100000000000000: begin
155                         end
156                         16'b1000000000000000: begin
157                         end
158                         default: begin
159                                 next_inc_next = 1'b1;
160                         end
161                         endcase
162                 end
163                 default: begin end
164                 endcase
165         end
166 endmodule
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