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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  OR1200's instruction fetch                                  ////
////                                                              ////
////  This file is part of the OpenRISC 1200 project              ////
////  http://www.opencores.org/cores/or1k/                        ////
////                                                              ////
////  Description                                                 ////
////  PC, instruction fetch, interface to IC.                     ////
////                                                              ////
////  To Do:                                                      ////
////   - make it smaller and faster                               ////
////                                                              ////
////  Author(s):                                                  ////
////      - Damjan Lampret, lampret@opencores.org                 ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source is distributed in the hope that it will be       ////
//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////
//// PURPOSE.  See the GNU Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
//
// CVS Revision History
//
// $Log: not supported by cvs2svn $
// Revision 1.1  2001/08/09 13:39:33  lampret
// Major clean-up.
//
//
 
// synopsys translate_off
`include "timescale.v"
// synopsys translate_on
`include "defines.v"
 
module ifetch(
        // Clock and reset
        clk, rst,
 
        // External i/f to IC
        ic_insn, ic_addr, ic_stall, ic_fetchop,
 
        // Internal i/f
        if_freeze, if_insn, if_pc, branch_op, except_type,
        branch_addrofs, lr_restor, flag, taken, binsn_addr, except_start,
        epcr, force_dslot_fetch, if_stall, branch_stall
);
 
//
// I/O
//
 
//
// Clock and reset
//
input                           clk;
input                           rst;
 
//
// External i/f to IC
//
input   [31:0]                   ic_insn;
output  [31:0]                   ic_addr;
output  [`FETCHOP_WIDTH-1:0]     ic_fetchop;
input                           ic_stall;
 
//
// Internal i/f
//
input                           if_freeze;
output  [31:0]                   if_insn;
output  [31:0]                   if_pc;
input   [`BRANCHOP_WIDTH-1:0]    branch_op;
input   [`EXCEPT_WIDTH-1:0]      except_type;
input   [31:2]                  branch_addrofs;
input   [31:0]                   lr_restor;
input                           flag;
input   [31:2]                  binsn_addr;
output                          taken;
input                           except_start;
input   [31:0]                   epcr;
input                           force_dslot_fetch;
output                          if_stall;
output                          branch_stall;
 
//
// Internal wires and regs
//
reg     [31:2]                  pcreg;
reg     [32:2]                  dslot_pc;
reg     [32:0]                   if_saved;
reg     [31:0]                   pcaddr;
reg     [31:0]                   pc_saved;
reg                             taken;  /* Set to in case of jump or taken branch */
 
//
// Current registered PC (corresponds to fetched instruction)
//
//assign if_pc = {pcreg[31:2], 2'b00};
assign if_pc = (if_saved[32]) ? pc_saved : ic_addr;
assign ic_addr = dslot_pc[32] ? {dslot_pc[31:2], 2'b00} : pcaddr;
assign branch_stall = dslot_pc[32] & taken;
//assign if_stall = ic_stall | (~branch_stall & taken);
assign if_stall = ic_stall;
 
//
// Control access to IC subsystem
//
assign ic_fetchop = (if_saved[32] & !if_stall) ? `FETCHOP_NOP : `FETCHOP_LW;
 
//
// Just fetched instruction
//
assign if_insn = (if_saved[32]) ? if_saved[31:0] : (ic_stall) ? 32'h1500FFFF : ic_insn;
 
//
// Delay slot PC saved
//
always @(posedge clk or posedge rst)
        if (rst)
                dslot_pc <= #1 31'h00000000;
//      else if (force_dslot_fetch)
//              dslot_pc <= #1 {1'b1, pcaddr[31:2]};
        else if (!ic_stall)
                dslot_pc <= #1 31'h00000000;
 
//
// Async calculation of new PC value. This value is used for addressing the IC.
//
always @(pcreg or branch_addrofs or binsn_addr or flag or branch_op or except_type
        or except_start or lr_restor or epcr) begin
        casex ({except_start, branch_op})       // synopsys parallel_case
                {1'b0, `BRANCHOP_NOP}: begin
                        pcaddr = {pcreg + 'd1, 2'b0};
                        taken = 1'b0;
                end
                {1'b0, `BRANCHOP_J}: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("%t: BRANCHOP_J: pcaddr <= branch_addrofs %h", $time, branch_addrofs);
// synopsys translate_on
`endif
                        pcaddr = {branch_addrofs, 2'b0};
                        taken = 1'b1;
                end
                {1'b0, `BRANCHOP_JR}: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("%t: BRANCHOP_JR: pcaddr <= lr_restor %h", $time, lr_restor);
// synopsys translate_on
`endif
                        pcaddr = lr_restor;
                        taken = 1'b1;
                end
                {1'b0, `BRANCHOP_BAL}: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("%t: BRANCHOP_BAL: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);
// synopsys translate_on
`endif
                        pcaddr = {binsn_addr + branch_addrofs, 2'b0};
                        taken = 1'b1;
                end
                {1'b0, `BRANCHOP_BF}:
                        if (flag) begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                                $display("%t: BRANCHOP_BF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);
// synopsys translate_on
`endif
                                pcaddr = {binsn_addr + branch_addrofs, 2'b0};
                                taken = 1'b1;
                        end
                        else begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                                $display("%t: BRANCHOP_BF: not taken", $time);
// synopsys translate_on
`endif
                                pcaddr = {pcreg + 'd1, 2'b0};
                                taken = 1'b0;
                        end
                {1'b0, `BRANCHOP_BNF}:
                        if (flag) begin
                                pcaddr = {pcreg + 'd1, 2'b0};
`ifdef OR1200_VERBOSE
// synopsys translate_off
                                $display("%t: BRANCHOP_BNF: not taken", $time);
// synopsys translate_on
`endif
                                taken = 1'b0;
                        end
                        else begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                                $display("%t: BRANCHOP_BNF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);
// synopsys translate_on
`endif
                                pcaddr = {binsn_addr + branch_addrofs, 2'b0};
                                taken = 1'b1;
                        end
                {1'b0, `BRANCHOP_RFE}: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("%t: BRANCHOP_RFE: pcaddr <= epcr %h", $time, epcr);
// synopsys translate_on
`endif
                        pcaddr = epcr;
                        taken = 1'b1;
                end
                default: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("Starting exception: %h.", except_type);
// synopsys translate_on
`endif
                        pcaddr = { 20'h0_0000, except_type, 8'h00};
                        taken = 1'b1;
                end
        endcase
end
 
//
// PC register
//
always @(posedge clk or posedge rst) begin
        if (rst)
                pcreg <= #1 30'd64;
        else if (!if_freeze && !ic_stall) begin
                pcreg <= #1 ic_addr[31:2];
`ifdef OR1200_VERBOSE
// synopsys translate_off
                $display("%t: pcreg incremented to %h", $time, {ic_addr[31:2], 2'b0});
// synopsys translate_on
`endif
        end
end
 
//
// Stores INSN when pipeline is frozen
//
always @(posedge clk or posedge rst)
        if (rst) begin
                if_saved <= #1 33'b0;
        end
        else if (if_freeze && !if_saved[32] && !ic_stall) begin  // && !taken
                if_saved <= #1 {1'b1, ic_insn};
`ifdef OR1200_VERBOSE
// synopsys translate_off
                $display("%t: if_saved <= %h", $time, {1'b1, ic_insn});
// synopsys translate_on
`endif
        end
        else if (!if_freeze) begin
                if_saved[32] <= #1 1'b0;
                if_saved[31:0] <= #1 32'h1500eeee;
`ifdef OR1200_VERBOSE
// synopsys translate_off
                $display("%t: if_saved[32] <= 0", $time);
// synopsys translate_on
`endif
        end
 
//
// Stores PC when pipeline is frozen
//
always @(posedge clk or posedge rst)
        if (rst) begin
                pc_saved <= #1 32'b0;
        end
        else if (if_freeze && !if_saved[32] && !ic_stall) begin  // && !taken
                pc_saved <= #1 ic_addr;
        end
        else if (!if_freeze) begin
                pc_saved <= #1 32'h00000000;
        end
 
endmodule

Line No.	Rev	Author	Line
1	168	lampret	`//////////////////////////////////////////////////////////////////////`
2			`//// ////`
3			`//// OR1200's instruction fetch ////`
4			`//// ////`
5			`//// This file is part of the OpenRISC 1200 project ////`
6			`//// http://www.opencores.org/cores/or1k/ ////`
7			`//// ////`
8			`//// Description ////`
9			`//// PC, instruction fetch, interface to IC. ////`
10			`//// ////`
11			`//// To Do: ////`
12			`//// - make it smaller and faster ////`
13			`//// ////`
14			`//// Author(s): ////`
15			`//// - Damjan Lampret, lampret@opencores.org ////`
16			`//// ////`
17			`//////////////////////////////////////////////////////////////////////`
18			`//// ////`
19			`//// Copyright (C) 2000 Authors and OPENCORES.ORG ////`
20			`//// ////`
21			`//// This source file may be used and distributed without ////`
22			`//// restriction provided that this copyright statement is not ////`
23			`//// removed from the file and that any derivative work contains ////`
24			`//// the original copyright notice and the associated disclaimer. ////`
25			`//// ////`
26			`//// This source file is free software; you can redistribute it ////`
27			`//// and/or modify it under the terms of the GNU Lesser General ////`
28			`//// Public License as published by the Free Software Foundation; ////`
29			`//// either version 2.1 of the License, or (at your option) any ////`
30			`//// later version. ////`
31			`//// ////`
32			`//// This source is distributed in the hope that it will be ////`
33			`//// useful, but WITHOUT ANY WARRANTY; without even the implied ////`
34			`//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////`
35			`//// PURPOSE. See the GNU Lesser General Public License for more ////`
36			`//// details. ////`
37			`//// ////`
38			`//// You should have received a copy of the GNU Lesser General ////`
39			`//// Public License along with this source; if not, download it ////`
40			`//// from http://www.opencores.org/lgpl.shtml ////`
41			`//// ////`
42			`//////////////////////////////////////////////////////////////////////`
43			`//`
44			`// CVS Revision History`
45			`//`
46			`// $Log: not supported by cvs2svn $`
47	203	lampret	`// Revision 1.1 2001/08/09 13:39:33 lampret`
48			`// Major clean-up.`
49	168	lampret	`//`
50	203	lampret	`//`
51	168	lampret
52	203	lampret	`// synopsys translate_off`
53	168	lampret	`include "timescale.v"
54	203	lampret	`// synopsys translate_on`
55	168	lampret	`include "defines.v"
56
57			`module ifetch(`
58			`// Clock and reset`
59			`clk, rst,`
60
61			`// External i/f to IC`
62	209	lampret	`ic_insn, ic_addr, ic_stall, ic_fetchop,`
63	168	lampret
64			`// Internal i/f`
65	205	lampret	`if_freeze, if_insn, if_pc, branch_op, except_type,`
66	168	lampret	`branch_addrofs, lr_restor, flag, taken, binsn_addr, except_start,`
67	203	lampret	`epcr, force_dslot_fetch, if_stall, branch_stall`
68	168	lampret	`);`
69
70			`//`
71			`// I/O`
72			`//`
73
74			`//`
75			`// Clock and reset`
76			`//`
77			`input clk;`
78			`input rst;`
79
80			`//`
81			`// External i/f to IC`
82			`//`
83			`input [31:0] ic_insn;`
84	203	lampret	`output [31:0] ic_addr;`
85			output [`FETCHOP_WIDTH-1:0] ic_fetchop;
86	168	lampret	`input ic_stall;`
87
88			`//`
89			`// Internal i/f`
90			`//`
91	205	lampret	`input if_freeze;`
92	168	lampret	`output [31:0] if_insn;`
93			`output [31:0] if_pc;`
94			input [`BRANCHOP_WIDTH-1:0] branch_op;
95			input [`EXCEPT_WIDTH-1:0] except_type;
96			`input [31:2] branch_addrofs;`
97			`input [31:0] lr_restor;`
98			`input flag;`
99			`input [31:2] binsn_addr;`
100			`output taken;`
101			`input except_start;`
102			`input [31:0] epcr;`
103	203	lampret	`input force_dslot_fetch;`
104			`output if_stall;`
105			`output branch_stall;`
106	168	lampret
107			`//`
108			`// Internal wires and regs`
109			`//`
110			`reg [31:2] pcreg;`
111	203	lampret	`reg [32:2] dslot_pc;`
112	168	lampret	`reg [32:0] if_saved;`
113	203	lampret	`reg [31:0] pcaddr;`
114			`reg [31:0] pc_saved;`
115	168	lampret	`reg taken; /* Set to in case of jump or taken branch */`
116
117			`//`
118			`// Current registered PC (corresponds to fetched instruction)`
119			`//`
120	203	lampret	`//assign if_pc = {pcreg[31:2], 2'b00};`
121			`assign if_pc = (if_saved[32]) ? pc_saved : ic_addr;`
122			`assign ic_addr = dslot_pc[32] ? {dslot_pc[31:2], 2'b00} : pcaddr;`
123			`assign branch_stall = dslot_pc[32] & taken;`
124			`//assign if_stall = ic_stall \| (~branch_stall & taken);`
125			`assign if_stall = ic_stall;`
126	168	lampret
127			`//`
128	203	lampret	`// Control access to IC subsystem`
129			`//`
130			assign ic_fetchop = (if_saved[32] & !if_stall) ? `FETCHOP_NOP : `FETCHOP_LW;
131
132			`//`
133	168	lampret	`// Just fetched instruction`
134			`//`
135	209	lampret	`assign if_insn = (if_saved[32]) ? if_saved[31:0] : (ic_stall) ? 32'h1500FFFF : ic_insn;`
136	168	lampret
137			`//`
138	203	lampret	`// Delay slot PC saved`
139			`//`
140			`always @(posedge clk or posedge rst)`
141			`if (rst)`
142			`dslot_pc <= #1 31'h00000000;`
143			`// else if (force_dslot_fetch)`
144			`// dslot_pc <= #1 {1'b1, pcaddr[31:2]};`
145			`else if (!ic_stall)`
146			`dslot_pc <= #1 31'h00000000;`
147
148			`//`
149	168	lampret	`// Async calculation of new PC value. This value is used for addressing the IC.`
150			`//`
151			`always @(pcreg or branch_addrofs or binsn_addr or flag or branch_op or except_type`
152			`or except_start or lr_restor or epcr) begin`
153			`casex ({except_start, branch_op}) // synopsys parallel_case`
154			{1'b0, `BRANCHOP_NOP}: begin
155	203	lampret	`pcaddr = {pcreg + 'd1, 2'b0};`
156			`taken = 1'b0;`
157	168	lampret	`end`
158			{1'b0, `BRANCHOP_J}: begin
159	203	lampret	`ifdef OR1200_VERBOSE
160			`// synopsys translate_off`
161			`$display("%t: BRANCHOP_J: pcaddr <= branch_addrofs %h", $time, branch_addrofs);`
162			`// synopsys translate_on`
163			`endif
164			`pcaddr = {branch_addrofs, 2'b0};`
165			`taken = 1'b1;`
166	168	lampret	`end`
167			{1'b0, `BRANCHOP_JR}: begin
168	203	lampret	`ifdef OR1200_VERBOSE
169			`// synopsys translate_off`
170			`$display("%t: BRANCHOP_JR: pcaddr <= lr_restor %h", $time, lr_restor);`
171			`// synopsys translate_on`
172			`endif
173			`pcaddr = lr_restor;`
174			`taken = 1'b1;`
175	168	lampret	`end`
176			{1'b0, `BRANCHOP_BAL}: begin
177	203	lampret	`ifdef OR1200_VERBOSE
178			`// synopsys translate_off`
179			`$display("%t: BRANCHOP_BAL: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
180			`// synopsys translate_on`
181			`endif
182			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
183			`taken = 1'b1;`
184	168	lampret	`end`
185			{1'b0, `BRANCHOP_BF}:
186			`if (flag) begin`
187	203	lampret	`ifdef OR1200_VERBOSE
188			`// synopsys translate_off`
189			`$display("%t: BRANCHOP_BF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
190			`// synopsys translate_on`
191			`endif
192			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
193			`taken = 1'b1;`
194	168	lampret	`end`
195			`else begin`
196	203	lampret	`ifdef OR1200_VERBOSE
197			`// synopsys translate_off`
198	168	lampret	`$display("%t: BRANCHOP_BF: not taken", $time);`
199	203	lampret	`// synopsys translate_on`
200			`endif
201			`pcaddr = {pcreg + 'd1, 2'b0};`
202			`taken = 1'b0;`
203	168	lampret	`end`
204			{1'b0, `BRANCHOP_BNF}:
205			`if (flag) begin`
206	203	lampret	`pcaddr = {pcreg + 'd1, 2'b0};`
207			`ifdef OR1200_VERBOSE
208			`// synopsys translate_off`
209	168	lampret	`$display("%t: BRANCHOP_BNF: not taken", $time);`
210	203	lampret	`// synopsys translate_on`
211			`endif
212			`taken = 1'b0;`
213	168	lampret	`end`
214			`else begin`
215	203	lampret	`ifdef OR1200_VERBOSE
216			`// synopsys translate_off`
217			`$display("%t: BRANCHOP_BNF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
218			`// synopsys translate_on`
219			`endif
220			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
221			`taken = 1'b1;`
222	168	lampret	`end`
223			{1'b0, `BRANCHOP_RFE}: begin
224	203	lampret	`ifdef OR1200_VERBOSE
225			`// synopsys translate_off`
226			`$display("%t: BRANCHOP_RFE: pcaddr <= epcr %h", $time, epcr);`
227			`// synopsys translate_on`
228			`endif
229			`pcaddr = epcr;`
230			`taken = 1'b1;`
231	168	lampret	`end`
232			`default: begin`
233	203	lampret	`ifdef OR1200_VERBOSE
234	168	lampret	`// synopsys translate_off`
235			`$display("Starting exception: %h.", except_type);`
236			`// synopsys translate_on`
237	203	lampret	`endif
238	209	lampret	`pcaddr = { 20'h0_0000, except_type, 8'h00};`
239	203	lampret	`taken = 1'b1;`
240	168	lampret	`end`
241			`endcase`
242			`end`
243
244			`//`
245			`// PC register`
246			`//`
247			`always @(posedge clk or posedge rst) begin`
248			`if (rst)`
249			`pcreg <= #1 30'd64;`
250	205	lampret	`else if (!if_freeze && !ic_stall) begin`
251	203	lampret	`pcreg <= #1 ic_addr[31:2];`
252			`ifdef OR1200_VERBOSE
253			`// synopsys translate_off`
254			`$display("%t: pcreg incremented to %h", $time, {ic_addr[31:2], 2'b0});`
255			`// synopsys translate_on`
256			`endif
257	168	lampret	`end`
258			`end`
259
260			`//`
261			`// Stores INSN when pipeline is frozen`
262			`//`
263			`always @(posedge clk or posedge rst)`
264			`if (rst) begin`
265			`if_saved <= #1 33'b0;`
266			`end`
267	205	lampret	`else if (if_freeze && !if_saved[32] && !ic_stall) begin // && !taken`
268	209	lampret	`if_saved <= #1 {1'b1, ic_insn};`
269	203	lampret	`ifdef OR1200_VERBOSE
270			`// synopsys translate_off`
271	209	lampret	`$display("%t: if_saved <= %h", $time, {1'b1, ic_insn});`
272	203	lampret	`// synopsys translate_on`
273			`endif
274	168	lampret	`end`
275	205	lampret	`else if (!if_freeze) begin`
276	168	lampret	`if_saved[32] <= #1 1'b0;`
277			`if_saved[31:0] <= #1 32'h1500eeee;`
278	203	lampret	`ifdef OR1200_VERBOSE
279			`// synopsys translate_off`
280	168	lampret	`$display("%t: if_saved[32] <= 0", $time);`
281	203	lampret	`// synopsys translate_on`
282			`endif
283	168	lampret	`end`
284
285	203	lampret	`//`
286			`// Stores PC when pipeline is frozen`
287			`//`
288			`always @(posedge clk or posedge rst)`
289			`if (rst) begin`
290			`pc_saved <= #1 32'b0;`
291			`end`
292	205	lampret	`else if (if_freeze && !if_saved[32] && !ic_stall) begin // && !taken`
293	203	lampret	`pc_saved <= #1 ic_addr;`
294			`end`
295	205	lampret	`else if (!if_freeze) begin`
296	203	lampret	`pc_saved <= #1 32'h00000000;`
297			`end`
298
299	168	lampret	`endmodule`

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