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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 1.1.1.1  2001/10/06 10:18:36  igorm
// no message
//
// 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,
        spr_dat_i, spr_pc_we
);
 
//
// 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;
input   [31:0]                   spr_dat_i;
input                           spr_pc_we;
 
//
// 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 or spr_pc_we or spr_dat_i) begin
        casex ({spr_pc_we, except_start, branch_op})    // synopsys parallel_case
                {2'b00, `BRANCHOP_NOP}: begin
                        pcaddr = {pcreg + 'd1, 2'b0};
                        taken = 1'b0;
                end
                {2'b00, `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
                {2'b00, `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
                {2'b00, `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
                {2'b00, `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
                {2'b00, `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
                {2'b00, `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
                {2'b01, 3'bxxx}: 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
                default: begin
`ifdef OR1200_VERBOSE
// synopsys translate_off
                        $display("l.mtspr writing into PC: %h.", spr_dat_i);
// synopsys translate_on
`endif
                        pcaddr = spr_dat_i;
                        taken = 1'b0;
                end
        endcase
end
 
//
// PC register
//
always @(posedge clk or posedge rst) begin
        if (rst)
                pcreg <= #1 30'd64;
        else if (spr_pc_we)
                pcreg <= #1 spr_dat_i[31:2];
        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

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[/] [or1k/] [branches/] [mp3_stable/] [or1200/] [rtl/] [verilog/] [ifetch.v] - Blame information for rev 215

Line No.	Rev	Author	Line
1	168	lampret
2	215	lampret	`//////////////////////////////////////////////////////////////////////`
3			`//// ////`
4			`//// OR1200's instruction fetch ////`
5			`//// ////`
6			`//// This file is part of the OpenRISC 1200 project ////`
7			`//// http://www.opencores.org/cores/or1k/ ////`
8			`//// ////`
9			`//// Description ////`
10			`//// PC, instruction fetch, interface to IC. ////`
11			`//// ////`
12			`//// To Do: ////`
13			`//// - make it smaller and faster ////`
14			`//// ////`
15			`//// Author(s): ////`
16			`//// - Damjan Lampret, lampret@opencores.org ////`
17			`//// ////`
18			`//////////////////////////////////////////////////////////////////////`
19			`//// ////`
20			`//// Copyright (C) 2000 Authors and OPENCORES.ORG ////`
21			`//// ////`
22			`//// This source file may be used and distributed without ////`
23			`//// restriction provided that this copyright statement is not ////`
24			`//// removed from the file and that any derivative work contains ////`
25			`//// the original copyright notice and the associated disclaimer. ////`
26			`//// ////`
27			`//// This source file is free software; you can redistribute it ////`
28			`//// and/or modify it under the terms of the GNU Lesser General ////`
29			`//// Public License as published by the Free Software Foundation; ////`
30			`//// either version 2.1 of the License, or (at your option) any ////`
31			`//// later version. ////`
32			`//// ////`
33			`//// This source is distributed in the hope that it will be ////`
34			`//// useful, but WITHOUT ANY WARRANTY; without even the implied ////`
35			`//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////`
36			`//// PURPOSE. See the GNU Lesser General Public License for more ////`
37			`//// details. ////`
38			`//// ////`
39			`//// You should have received a copy of the GNU Lesser General ////`
40			`//// Public License along with this source; if not, download it ////`
41			`//// from http://www.opencores.org/lgpl.shtml ////`
42			`//// ////`
43			`//////////////////////////////////////////////////////////////////////`
44			`//`
45			`// CVS Revision History`
46			`//`
47			`// $Log: not supported by cvs2svn $`
48			`// Revision 1.1.1.1 2001/10/06 10:18:36 igorm`
49			`// no message`
50			`//`
51			`// Revision 1.1 2001/08/09 13:39:33 lampret`
52			`// Major clean-up.`
53			`//`
54			`//`
55
56			`// synopsys translate_off`
57			`include "timescale.v"
58			`// synopsys translate_on`
59			`include "defines.v"
60
61			`module ifetch(`
62			`// Clock and reset`
63			`clk, rst,`
64
65			`// External i/f to IC`
66			`ic_insn, ic_addr, ic_stall, ic_fetchop,`
67
68			`// Internal i/f`
69			`if_freeze, if_insn, if_pc, branch_op, except_type,`
70			`branch_addrofs, lr_restor, flag, taken, binsn_addr, except_start,`
71			`epcr, force_dslot_fetch, if_stall, branch_stall,`
72			`spr_dat_i, spr_pc_we`
73			`);`
74
75			`//`
76			`// I/O`
77			`//`
78
79			`//`
80			`// Clock and reset`
81			`//`
82			`input clk;`
83			`input rst;`
84
85			`//`
86			`// External i/f to IC`
87			`//`
88			`input [31:0] ic_insn;`
89			`output [31:0] ic_addr;`
90			output [`FETCHOP_WIDTH-1:0] ic_fetchop;
91			`input ic_stall;`
92
93			`//`
94			`// Internal i/f`
95			`//`
96			`input if_freeze;`
97			`output [31:0] if_insn;`
98			`output [31:0] if_pc;`
99			input [`BRANCHOP_WIDTH-1:0] branch_op;
100			input [`EXCEPT_WIDTH-1:0] except_type;
101			`input [31:2] branch_addrofs;`
102			`input [31:0] lr_restor;`
103			`input flag;`
104			`input [31:2] binsn_addr;`
105			`output taken;`
106			`input except_start;`
107			`input [31:0] epcr;`
108			`input force_dslot_fetch;`
109			`output if_stall;`
110			`output branch_stall;`
111			`input [31:0] spr_dat_i;`
112			`input spr_pc_we;`
113
114			`//`
115			`// Internal wires and regs`
116			`//`
117			`reg [31:2] pcreg;`
118			`reg [32:2] dslot_pc;`
119			`reg [32:0] if_saved;`
120			`reg [31:0] pcaddr;`
121			`reg [31:0] pc_saved;`
122			`reg taken; /* Set to in case of jump or taken branch */`
123
124			`//`
125			`// Current registered PC (corresponds to fetched instruction)`
126			`//`
127			`//assign if_pc = {pcreg[31:2], 2'b00};`
128			`assign if_pc = (if_saved[32]) ? pc_saved : ic_addr;`
129			`assign ic_addr = dslot_pc[32] ? {dslot_pc[31:2], 2'b00} : pcaddr;`
130			`assign branch_stall = dslot_pc[32] & taken;`
131			`//assign if_stall = ic_stall \| (~branch_stall & taken);`
132			`assign if_stall = ic_stall;`
133
134			`//`
135			`// Control access to IC subsystem`
136			`//`
137			assign ic_fetchop = (if_saved[32] & !if_stall) ? `FETCHOP_NOP : `FETCHOP_LW;
138
139			`//`
140			`// Just fetched instruction`
141			`//`
142			`assign if_insn = (if_saved[32]) ? if_saved[31:0] : (ic_stall) ? 32'h1500FFFF : ic_insn;`
143
144			`//`
145			`// Delay slot PC saved`
146			`//`
147			`always @(posedge clk or posedge rst)`
148			`if (rst)`
149			`dslot_pc <= #1 31'h00000000;`
150			`// else if (force_dslot_fetch)`
151			`// dslot_pc <= #1 {1'b1, pcaddr[31:2]};`
152			`else if (!ic_stall)`
153			`dslot_pc <= #1 31'h00000000;`
154
155			`//`
156			`// Async calculation of new PC value. This value is used for addressing the IC.`
157			`//`
158			`always @(pcreg or branch_addrofs or binsn_addr or flag or branch_op or except_type`
159			`or except_start or lr_restor or epcr or spr_pc_we or spr_dat_i) begin`
160			`casex ({spr_pc_we, except_start, branch_op}) // synopsys parallel_case`
161			{2'b00, `BRANCHOP_NOP}: begin
162			`pcaddr = {pcreg + 'd1, 2'b0};`
163			`taken = 1'b0;`
164			`end`
165			{2'b00, `BRANCHOP_J}: begin
166			`ifdef OR1200_VERBOSE
167			`// synopsys translate_off`
168			`$display("%t: BRANCHOP_J: pcaddr <= branch_addrofs %h", $time, branch_addrofs);`
169			`// synopsys translate_on`
170			`endif
171			`pcaddr = {branch_addrofs, 2'b0};`
172			`taken = 1'b1;`
173			`end`
174			{2'b00, `BRANCHOP_JR}: begin
175			`ifdef OR1200_VERBOSE
176			`// synopsys translate_off`
177			`$display("%t: BRANCHOP_JR: pcaddr <= lr_restor %h", $time, lr_restor);`
178			`// synopsys translate_on`
179			`endif
180			`pcaddr = lr_restor;`
181			`taken = 1'b1;`
182			`end`
183			{2'b00, `BRANCHOP_BAL}: begin
184			`ifdef OR1200_VERBOSE
185			`// synopsys translate_off`
186			`$display("%t: BRANCHOP_BAL: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
187			`// synopsys translate_on`
188			`endif
189			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
190			`taken = 1'b1;`
191			`end`
192			{2'b00, `BRANCHOP_BF}:
193			`if (flag) begin`
194			`ifdef OR1200_VERBOSE
195			`// synopsys translate_off`
196			`$display("%t: BRANCHOP_BF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
197			`// synopsys translate_on`
198			`endif
199			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
200			`taken = 1'b1;`
201			`end`
202			`else begin`
203			`ifdef OR1200_VERBOSE
204			`// synopsys translate_off`
205			`$display("%t: BRANCHOP_BF: not taken", $time);`
206			`// synopsys translate_on`
207			`endif
208			`pcaddr = {pcreg + 'd1, 2'b0};`
209			`taken = 1'b0;`
210			`end`
211			{2'b00, `BRANCHOP_BNF}:
212			`if (flag) begin`
213			`pcaddr = {pcreg + 'd1, 2'b0};`
214			`ifdef OR1200_VERBOSE
215			`// synopsys translate_off`
216			`$display("%t: BRANCHOP_BNF: not taken", $time);`
217			`// synopsys translate_on`
218			`endif
219			`taken = 1'b0;`
220			`end`
221			`else begin`
222			`ifdef OR1200_VERBOSE
223			`// synopsys translate_off`
224			`$display("%t: BRANCHOP_BNF: pcaddr %h = binsn_addr %h + branch_addrofs %h", $time, binsn_addr + branch_addrofs, binsn_addr, branch_addrofs);`
225			`// synopsys translate_on`
226			`endif
227			`pcaddr = {binsn_addr + branch_addrofs, 2'b0};`
228			`taken = 1'b1;`
229			`end`
230			{2'b00, `BRANCHOP_RFE}: begin
231			`ifdef OR1200_VERBOSE
232			`// synopsys translate_off`
233			`$display("%t: BRANCHOP_RFE: pcaddr <= epcr %h", $time, epcr);`
234			`// synopsys translate_on`
235			`endif
236			`pcaddr = epcr;`
237			`taken = 1'b1;`
238			`end`
239			`{2'b01, 3'bxxx}: begin`
240			`ifdef OR1200_VERBOSE
241			`// synopsys translate_off`
242			`$display("Starting exception: %h.", except_type);`
243			`// synopsys translate_on`
244			`endif
245			`pcaddr = { 20'h0_0000, except_type, 8'h00};`
246			`taken = 1'b1;`
247			`end`
248			`default: begin`
249			`ifdef OR1200_VERBOSE
250			`// synopsys translate_off`
251			`$display("l.mtspr writing into PC: %h.", spr_dat_i);`
252			`// synopsys translate_on`
253			`endif
254			`pcaddr = spr_dat_i;`
255			`taken = 1'b0;`
256			`end`
257			`endcase`
258			`end`
259
260			`//`
261			`// PC register`
262			`//`
263			`always @(posedge clk or posedge rst) begin`
264			`if (rst)`
265			`pcreg <= #1 30'd64;`
266			`else if (spr_pc_we)`
267			`pcreg <= #1 spr_dat_i[31:2];`
268			`else if (!if_freeze && !ic_stall) begin`
269			`pcreg <= #1 ic_addr[31:2];`
270			`ifdef OR1200_VERBOSE
271			`// synopsys translate_off`
272			`$display("%t: pcreg incremented to %h", $time, {ic_addr[31:2], 2'b0});`
273			`// synopsys translate_on`
274			`endif
275			`end`
276			`end`
277
278			`//`
279			`// Stores INSN when pipeline is frozen`
280			`//`
281			`always @(posedge clk or posedge rst)`
282			`if (rst) begin`
283			`if_saved <= #1 33'b0;`
284			`end`
285			`else if (if_freeze && !if_saved[32] && !ic_stall) begin // && !taken`
286			`if_saved <= #1 {1'b1, ic_insn};`
287			`ifdef OR1200_VERBOSE
288			`// synopsys translate_off`
289			`$display("%t: if_saved <= %h", $time, {1'b1, ic_insn});`
290			`// synopsys translate_on`
291			`endif
292			`end`
293			`else if (!if_freeze) begin`
294			`if_saved[32] <= #1 1'b0;`
295			`if_saved[31:0] <= #1 32'h1500eeee;`
296			`ifdef OR1200_VERBOSE
297			`// synopsys translate_off`
298			`$display("%t: if_saved[32] <= 0", $time);`
299			`// synopsys translate_on`
300			`endif
301			`end`
302
303			`//`
304			`// Stores PC when pipeline is frozen`
305			`//`
306			`always @(posedge clk or posedge rst)`
307			`if (rst) begin`
308			`pc_saved <= #1 32'b0;`
309			`end`
310			`else if (if_freeze && !if_saved[32] && !ic_stall) begin // && !taken`
311			`pc_saved <= #1 ic_addr;`
312			`end`
313			`else if (!if_freeze) begin`
314			`pc_saved <= #1 32'h00000000;`
315			`end`
316
317			`endmodule`