3 * Copyright 2018 Jacob Lifshay
5 * Permission is hereby granted, free of charge, to any person obtaining a copy
6 * of this software and associated documentation files (the "Software"), to deal
7 * in the Software without restriction, including without limitation the rights
8 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 * copies of the Software, and to permit persons to whom the Software is
10 * furnished to do so, subject to the following conditions:
12 * The above copyright notice and this permission notice shall be included in all
13 * copies or substantial portions of the Software.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
30 from migen
.fhdl
import verilog
31 from migen
.fhdl
.structure
import _Operator
33 from riscvdefs
import *
36 class MemoryInterface
:
37 fetch_address
= Signal(32, name
="memory_interface_fetch_address") # XXX [2:]
38 fetch_data
= Signal(32, name
="memory_interface_fetch_data")
39 fetch_valid
= Signal(name
="memory_interface_fetch_valid")
40 rw_address
= Signal(32, name
="memory_interface_rw_address") # XXX [2:]
41 rw_byte_mask
= Signal(4, name
="memory_interface_rw_byte_mask")
42 rw_read_not_write
= Signal(name
="memory_interface_rw_read_not_write")
43 rw_active
= Signal(name
="memory_interface_rw_active")
44 rw_data_in
= Signal(32, name
="memory_interface_rw_data_in")
45 rw_data_out
= Signal(32, name
="memory_interface_rw_data_out")
46 rw_address_valid
= Signal(name
="memory_interface_rw_address_valid")
47 rw_wait
= Signal(name
="memory_interface_rw_wait")
54 def get_ls_misaligned(self
, ls
, funct3
, load_store_address_low_2
):
55 return Case(funct3
[:2],
56 { F3
.sb
: ls
.eq(Constant(0)),
57 F3
.sh
: ls
.eq(load_store_address_low_2
[0] != 0),
58 F3
.sw
: ls
.eq(load_store_address_low_2
[0:2] != Constant(0, 2)),
59 "default": ls
.eq(Constant(1))
62 def get_lsbm(self
, decoder_funct3
):
63 return Cat(Constant(1),
64 Mux((decoder_funct3
[1] | decoder_funct3
[0]),
65 Constant(1), Constant(0)),
66 Mux((decoder_funct3
[1]),
67 Constant(0b11, 2), Constant(0, 2)))
70 #self.clk = ClockSignal()
71 #self.reset = ResetSignal()
72 self
.tty_write
= Signal()
73 self
.tty_write_data
= Signal(8)
74 self
.tty_write_busy
= Signal()
75 self
.switch_2
= Signal()
76 self
.switch_3
= Signal()
80 ram_size
= Constant(0x8000)
81 ram_start
= Constant(0x10000, 32)
82 reset_vector
= Signal(32)
85 reset_vector
.eq(ram_start
)
86 mtvec
.eq(ram_start
+ 0x40)
90 l
.append(Signal(32, name
="register%d" % i
))
93 mi
= MemoryInterface()
95 mii
= Instance("cpu_memory_interface", name
="memory_instance",
96 p_ram_size
= ram_size
,
97 p_ram_start
= ram_start
,
100 i_fetch_address
= mi
.fetch_address
,
101 o_fetch_data
= mi
.fetch_data
,
102 o_fetch_valid
= mi
.fetch_valid
,
103 i_rw_address
= mi
.rw_address
,
104 i_rw_byte_mask
= mi
.rw_byte_mask
,
105 i_rw_read_not_write
= mi
.rw_read_not_write
,
106 i_rw_active
= mi
.rw_active
,
107 i_rw_data_in
= mi
.rw_data_in
,
108 o_rw_data_out
= mi
.rw_data_out
,
109 o_rw_address_valid
= mi
.rw_address_valid
,
110 o_rw_wait
= mi
.rw_wait
,
111 o_tty_write
= self
.tty_write
,
112 o_tty_write_data
= self
.tty_write_data
,
113 i_tty_write_busy
= self
.tty_write_busy
,
114 i_switch_2
= self
.switch_2
,
115 i_switch_3
= self
.switch_3
,
116 o_led_1
= self
.led_1
,
121 fetch_act
= Signal(fetch_action
)
122 fetch_target_pc
= Signal(32)
123 fetch_output_pc
= Signal(32)
124 fetch_output_instruction
= Signal(32)
125 fetch_output_st
= Signal(fetch_output_state
)
127 fs
= Instance("CPUFetchStage", name
="fetch_stage",
130 o_memory_interface_fetch_address
= mi
.fetch_address
,
131 i_memory_interface_fetch_data
= mi
.fetch_data
,
132 i_memory_interface_fetch_valid
= mi
.fetch_valid
,
133 i_fetch_action
= fetch_act
,
134 i_target_pc
= fetch_target_pc
,
135 o_output_pc
= fetch_output_pc
,
136 o_output_instruction
= fetch_output_instruction
,
137 o_output_state
= fetch_output_st
,
138 i_reset_vector
= reset_vector
,
143 decoder_funct7
= Signal(7)
144 decoder_funct3
= Signal(3)
145 decoder_rd
= Signal(5)
146 decoder_rs1
= Signal(5)
147 decoder_rs2
= Signal(5)
148 decoder_immediate
= Signal(32)
149 decoder_opcode
= Signal(7)
150 decode_act
= Signal(decode_action
)
152 cd
= Instance("CPUDecoder", name
="decoder",
153 i_instruction
= fetch_output_instruction
,
154 o_funct7
= decoder_funct7
,
155 o_funct3
= decoder_funct3
,
159 o_immediate
= decoder_immediate
,
160 o_opcode
= decoder_opcode
,
161 o_decode_action
= decode_act
165 register_rs1
= Signal(32)
166 register_rs2
= Signal(32)
167 self
.comb
+= If(decoder_rs1
== 0,
170 register_rs1
.eq(registers
[decoder_rs1
-1]))
171 self
.comb
+= If(decoder_rs2
== 0,
174 register_rs2
.eq(registers
[decoder_rs2
-1]))
176 load_store_address
= Signal(32)
177 load_store_address_low_2
= Signal(2)
179 self
.comb
+= load_store_address
.eq(decoder_immediate
+ register_rs1
)
180 self
.comb
+= load_store_address_low_2
.eq(
181 decoder_immediate
[:2] + register_rs1
[:2])
183 load_store_misaligned
= Signal()
185 lsa
= self
.get_ls_misaligned(load_store_misaligned
, decoder_funct3
,
186 load_store_address_low_2
)
189 # XXX rwaddr not 31:2 any more
190 self
.comb
+= mi
.rw_address
.eq(load_store_address
[2:])
192 unshifted_load_store_byte_mask
= Signal(4)
194 self
.comb
+= unshifted_load_store_byte_mask
.eq(self
.get_lsbm(
197 # XXX yuck. this will cause migen simulation to fail
198 # (however conversion to verilog works)
199 self
.comb
+= mi
.rw_byte_mask
.eq(
200 _Operator("<<", [unshifted_load_store_byte_mask
,
201 load_store_address_low_2
]))
204 b3
= Mux(load_store_address_low_2
[1],
205 Mux(load_store_address_low_2
[0], register_rs2
[0:8],
207 Mux(load_store_address_low_2
[0], register_rs2
[16:24],
208 register_rs2
[24:32]))
209 b2
= Mux(load_store_address_low_2
[1], register_rs2
[0:8],
211 b1
= Mux(load_store_address_low_2
[0], register_rs2
[0:8],
213 b0
= register_rs2
[0:8]
215 self
.comb
+= mi
.rw_data_in
.eq(Cat(b0
, b1
, b2
, b3
))
218 unmasked_loaded_value
= Signal(32)
220 b0
= Mux(load_store_address_low_2
[1],
221 Mux(load_store_address_low_2
[0], mi
.rw_data_out
[24:32],
222 mi
.rw_data_out
[16:24]),
223 Mux(load_store_address_low_2
[0], mi
.rw_data_out
[15:8],
224 mi
.rw_data_out
[0:8]))
225 b1
= Mux(load_store_address_low_2
[1], mi
.rw_data_out
[24:31],
226 mi
.rw_data_out
[8:16])
227 b23
= mi
.rw_data_out
[16:32]
229 self
.comb
+= unmasked_loaded_value
.eq(Cat(b0
, b1
, b23
))
231 if __name__
== "__main__":
233 print(verilog
.convert(example
,
236 example
.tty_write_data
,
237 example
.tty_write_busy
,
246 wire [31:0] loaded_value;
248 assign loaded_value[7:0] = unmasked_loaded_value[7:0];
249 assign loaded_value[15:8] = decoder_funct3[1:0] == 0 ? ({8{~decoder_funct3[2] & unmasked_loaded_value[7]}}) : unmasked_loaded_value[15:8];
250 assign loaded_value[31:16] = decoder_funct3[1] == 0 ? ({16{~decoder_funct3[2] & (decoder_funct3[0] ? unmasked_loaded_value[15] : unmasked_loaded_value[7])}}) : unmasked_loaded_value[31:16];
252 assign memory_interface_rw_active = ~reset
253 & (fetch_output_state == `fetch_output_state_valid)
254 & ~load_store_misaligned
255 & ((decode_action & (`decode_action_load | `decode_action_store)) != 0);
257 assign memory_interface_rw_read_not_write = ~decoder_opcode[5];
259 wire [31:0] alu_a = register_rs1;
260 wire [31:0] alu_b = decoder_opcode[5] ? register_rs2 : decoder_immediate;
261 wire [31:0] alu_result;
264 .funct7(decoder_funct7),
265 .funct3(decoder_funct3),
266 .opcode(decoder_opcode),
272 wire [31:0] lui_auipc_result = decoder_opcode[5] ? decoder_immediate : decoder_immediate + fetch_output_pc;
274 assign fetch_target_pc[31:1] = ((decoder_opcode != `opcode_jalr ? fetch_output_pc[31:1] : register_rs1[31:1]) + decoder_immediate[31:1]);
275 assign fetch_target_pc[0] = 0;
277 wire misaligned_jump_target = fetch_target_pc[1];
279 wire [31:0] branch_arg_a = {register_rs1[31] ^ ~decoder_funct3[1], register_rs1[30:0]};
280 wire [31:0] branch_arg_b = {register_rs2[31] ^ ~decoder_funct3[1], register_rs2[30:0]};
282 wire branch_taken = decoder_funct3[0] ^ (decoder_funct3[2] ? branch_arg_a < branch_arg_b : branch_arg_a == branch_arg_b);
284 reg [31:0] mcause = 0;
285 reg [31:0] mepc = 32'hXXXXXXXX;
286 reg [31:0] mscratch = 32'hXXXXXXXX;
288 reg mstatus_mpie = 1'bX;
290 parameter mstatus_mprv = 0;
291 parameter mstatus_tsr = 0;
292 parameter mstatus_tw = 0;
293 parameter mstatus_tvm = 0;
294 parameter mstatus_mxr = 0;
295 parameter mstatus_sum = 0;
296 parameter mstatus_xs = 0;
297 parameter mstatus_fs = 0;
298 parameter mstatus_mpp = 2'b11;
299 parameter mstatus_spp = 0;
300 parameter mstatus_spie = 0;
301 parameter mstatus_upie = 0;
302 parameter mstatus_sie = 0;
303 parameter mstatus_uie = 0;
308 parameter mie_seie = 0;
309 parameter mie_ueie = 0;
310 parameter mie_stie = 0;
311 parameter mie_utie = 0;
312 parameter mie_ssie = 0;
313 parameter mie_usie = 0;
315 task reset_to_initial;
319 mscratch = 32'hXXXXXXXX;
325 registers['h01] <= 32'hXXXXXXXX;
326 registers['h02] <= 32'hXXXXXXXX;
327 registers['h03] <= 32'hXXXXXXXX;
328 registers['h04] <= 32'hXXXXXXXX;
329 registers['h05] <= 32'hXXXXXXXX;
330 registers['h06] <= 32'hXXXXXXXX;
331 registers['h07] <= 32'hXXXXXXXX;
332 registers['h08] <= 32'hXXXXXXXX;
333 registers['h09] <= 32'hXXXXXXXX;
334 registers['h0A] <= 32'hXXXXXXXX;
335 registers['h0B] <= 32'hXXXXXXXX;
336 registers['h0C] <= 32'hXXXXXXXX;
337 registers['h0D] <= 32'hXXXXXXXX;
338 registers['h0E] <= 32'hXXXXXXXX;
339 registers['h0F] <= 32'hXXXXXXXX;
340 registers['h10] <= 32'hXXXXXXXX;
341 registers['h11] <= 32'hXXXXXXXX;
342 registers['h12] <= 32'hXXXXXXXX;
343 registers['h13] <= 32'hXXXXXXXX;
344 registers['h14] <= 32'hXXXXXXXX;
345 registers['h15] <= 32'hXXXXXXXX;
346 registers['h16] <= 32'hXXXXXXXX;
347 registers['h17] <= 32'hXXXXXXXX;
348 registers['h18] <= 32'hXXXXXXXX;
349 registers['h19] <= 32'hXXXXXXXX;
350 registers['h1A] <= 32'hXXXXXXXX;
351 registers['h1B] <= 32'hXXXXXXXX;
352 registers['h1C] <= 32'hXXXXXXXX;
353 registers['h1D] <= 32'hXXXXXXXX;
354 registers['h1E] <= 32'hXXXXXXXX;
355 registers['h1F] <= 32'hXXXXXXXX;
359 task write_register(input [4:0] register_number, input [31:0] value);
361 if(register_number != 0)
362 registers[register_number] <= value;
366 function [31:0] evaluate_csr_funct3_operation(input [2:0] funct3, input [31:0] previous_value, input [31:0] written_value);
369 `funct3_csrrw, `funct3_csrrwi:
370 evaluate_csr_funct3_operation = written_value;
371 `funct3_csrrs, `funct3_csrrsi:
372 evaluate_csr_funct3_operation = written_value | previous_value;
373 `funct3_csrrc, `funct3_csrrci:
374 evaluate_csr_funct3_operation = ~written_value & previous_value;
376 evaluate_csr_funct3_operation = 32'hXXXXXXXX;
381 parameter misa_a = 1'b0;
382 parameter misa_b = 1'b0;
383 parameter misa_c = 1'b0;
384 parameter misa_d = 1'b0;
385 parameter misa_e = 1'b0;
386 parameter misa_f = 1'b0;
387 parameter misa_g = 1'b0;
388 parameter misa_h = 1'b0;
389 parameter misa_i = 1'b1;
390 parameter misa_j = 1'b0;
391 parameter misa_k = 1'b0;
392 parameter misa_l = 1'b0;
393 parameter misa_m = 1'b0;
394 parameter misa_n = 1'b0;
395 parameter misa_o = 1'b0;
396 parameter misa_p = 1'b0;
397 parameter misa_q = 1'b0;
398 parameter misa_r = 1'b0;
399 parameter misa_s = 1'b0;
400 parameter misa_t = 1'b0;
401 parameter misa_u = 1'b0;
402 parameter misa_v = 1'b0;
403 parameter misa_w = 1'b0;
404 parameter misa_x = 1'b0;
405 parameter misa_y = 1'b0;
406 parameter misa_z = 1'b0;
437 parameter mvendorid = 32'b0;
438 parameter marchid = 32'b0;
439 parameter mimpid = 32'b0;
440 parameter mhartid = 32'b0;
442 function [31:0] make_mstatus(input mstatus_tsr,
448 input [1:0] mstatus_xs,
449 input [1:0] mstatus_fs,
450 input [1:0] mstatus_mpp,
459 make_mstatus = {(mstatus_xs == 2'b11) | (mstatus_fs == 2'b11),
483 wire mip_meip = 0; // TODO: implement external interrupts
484 parameter mip_seip = 0;
485 parameter mip_ueip = 0;
486 wire mip_mtip = 0; // TODO: implement timer interrupts
487 parameter mip_stip = 0;
488 parameter mip_utip = 0;
489 parameter mip_msip = 0;
490 parameter mip_ssip = 0;
491 parameter mip_usip = 0;
493 wire csr_op_is_valid;
495 function `fetch_action get_fetch_action(
496 input `fetch_output_state fetch_output_state,
497 input `decode_action decode_action,
498 input load_store_misaligned,
499 input memory_interface_rw_address_valid,
500 input memory_interface_rw_wait,
502 input misaligned_jump_target,
503 input csr_op_is_valid
506 case(fetch_output_state)
507 `fetch_output_state_empty:
508 get_fetch_action = `fetch_action_default;
509 `fetch_output_state_trap:
510 get_fetch_action = `fetch_action_ack_trap;
511 `fetch_output_state_valid: begin
512 if((decode_action & `decode_action_trap_illegal_instruction) != 0) begin
513 get_fetch_action = `fetch_action_error_trap;
515 else if((decode_action & `decode_action_trap_ecall_ebreak) != 0) begin
516 get_fetch_action = `fetch_action_noerror_trap;
518 else if((decode_action & (`decode_action_load | `decode_action_store)) != 0) begin
519 if(load_store_misaligned | ~memory_interface_rw_address_valid) begin
520 get_fetch_action = `fetch_action_error_trap;
522 else if(memory_interface_rw_wait) begin
523 get_fetch_action = `fetch_action_wait;
526 get_fetch_action = `fetch_action_default;
529 else if((decode_action & `decode_action_fence_i) != 0) begin
530 get_fetch_action = `fetch_action_fence;
532 else if((decode_action & `decode_action_branch) != 0) begin
533 if(branch_taken) begin
534 if(misaligned_jump_target) begin
535 get_fetch_action = `fetch_action_error_trap;
538 get_fetch_action = `fetch_action_jump;
543 get_fetch_action = `fetch_action_default;
546 else if((decode_action & (`decode_action_jal | `decode_action_jalr)) != 0) begin
547 if(misaligned_jump_target) begin
548 get_fetch_action = `fetch_action_error_trap;
551 get_fetch_action = `fetch_action_jump;
554 else if((decode_action & `decode_action_csr) != 0) begin
556 get_fetch_action = `fetch_action_default;
558 get_fetch_action = `fetch_action_error_trap;
561 get_fetch_action = `fetch_action_default;
565 get_fetch_action = 32'hXXXXXXXX;
570 assign fetch_action = get_fetch_action(
573 load_store_misaligned,
574 memory_interface_rw_address_valid,
575 memory_interface_rw_wait,
577 misaligned_jump_target,
583 mstatus_mpie = mstatus_mie;
585 mepc = (fetch_action == `fetch_action_noerror_trap) ? fetch_output_pc + 4 : fetch_output_pc;
586 if(fetch_action == `fetch_action_ack_trap) begin
587 mcause = `cause_instruction_access_fault;
589 else if((decode_action & `decode_action_trap_illegal_instruction) != 0) begin
590 mcause = `cause_illegal_instruction;
592 else if((decode_action & `decode_action_trap_ecall_ebreak) != 0) begin
593 mcause = decoder_immediate[0] ? `cause_machine_environment_call : `cause_breakpoint;
595 else if((decode_action & `decode_action_load) != 0) begin
596 if(load_store_misaligned)
597 mcause = `cause_load_address_misaligned;
599 mcause = `cause_load_access_fault;
601 else if((decode_action & `decode_action_store) != 0) begin
602 if(load_store_misaligned)
603 mcause = `cause_store_amo_address_misaligned;
605 mcause = `cause_store_amo_access_fault;
607 else if((decode_action & (`decode_action_branch | `decode_action_jal | `decode_action_jalr)) != 0) begin
608 mcause = `cause_instruction_address_misaligned;
611 mcause = `cause_illegal_instruction;
616 wire [11:0] csr_number = decoder_immediate;
617 wire [31:0] csr_input_value = decoder_funct3[2] ? decoder_rs1 : register_rs1;
618 wire csr_reads = decoder_funct3[1] | (decoder_rd != 0);
619 wire csr_writes = ~decoder_funct3[1] | (decoder_rs1 != 0);
621 function get_csr_op_is_valid(input [11:0] csr_number, input csr_reads, input csr_writes);
652 get_csr_op_is_valid = 0;
663 get_csr_op_is_valid = ~csr_writes;
672 get_csr_op_is_valid = 1;
679 // TODO: CSRs not implemented yet
680 get_csr_op_is_valid = 0;
685 assign csr_op_is_valid = get_csr_op_is_valid(csr_number, csr_reads, csr_writes);
687 wire [63:0] cycle_counter = 0; // TODO: implement cycle_counter
688 wire [63:0] time_counter = 0; // TODO: implement time_counter
689 wire [63:0] instret_counter = 0; // TODO: implement instret_counter
691 always @(posedge clk) begin:main_block
696 case(fetch_output_state)
697 `fetch_output_state_empty: begin
699 `fetch_output_state_trap: begin
702 `fetch_output_state_valid: begin:valid
703 if((fetch_action == `fetch_action_error_trap) | (fetch_action == `fetch_action_noerror_trap)) begin
706 else if((decode_action & `decode_action_load) != 0) begin
707 if(~memory_interface_rw_wait)
708 write_register(decoder_rd, loaded_value);
710 else if((decode_action & `decode_action_op_op_imm) != 0) begin
711 write_register(decoder_rd, alu_result);
713 else if((decode_action & `decode_action_lui_auipc) != 0) begin
714 write_register(decoder_rd, lui_auipc_result);
716 else if((decode_action & (`decode_action_jal | `decode_action_jalr)) != 0) begin
717 write_register(decoder_rd, fetch_output_pc + 4);
719 else if((decode_action & `decode_action_csr) != 0) begin:csr
720 reg [31:0] csr_output_value;
721 reg [31:0] csr_written_value;
722 csr_output_value = 32'hXXXXXXXX;
723 csr_written_value = 32'hXXXXXXXX;
726 csr_output_value = cycle_counter[31:0];
729 csr_output_value = time_counter[31:0];
732 csr_output_value = instret_counter[31:0];
735 csr_output_value = cycle_counter[63:32];
738 csr_output_value = time_counter[63:32];
741 csr_output_value = instret_counter[63:32];
743 `csr_mvendorid: begin
744 csr_output_value = mvendorid;
747 csr_output_value = marchid;
750 csr_output_value = mimpid;
753 csr_output_value = mhartid;
756 csr_output_value = misa;
759 csr_output_value = make_mstatus(mstatus_tsr,
775 csr_written_value = evaluate_csr_funct3_operation(decoder_funct3, csr_output_value, csr_input_value);
777 mstatus_mpie = csr_written_value[7];
778 mstatus_mie = csr_written_value[3];
782 csr_output_value = 0;
783 csr_output_value[11] = mie_meie;
784 csr_output_value[9] = mie_seie;
785 csr_output_value[8] = mie_ueie;
786 csr_output_value[7] = mie_mtie;
787 csr_output_value[5] = mie_stie;
788 csr_output_value[4] = mie_utie;
789 csr_output_value[3] = mie_msie;
790 csr_output_value[1] = mie_ssie;
791 csr_output_value[0] = mie_usie;
792 csr_written_value = evaluate_csr_funct3_operation(decoder_funct3, csr_output_value, csr_input_value);
794 mie_meie = csr_written_value[11];
795 mie_mtie = csr_written_value[7];
796 mie_msie = csr_written_value[3];
800 csr_output_value = mtvec;
803 csr_output_value = mscratch;
804 csr_written_value = evaluate_csr_funct3_operation(decoder_funct3, csr_output_value, csr_input_value);
806 mscratch = csr_written_value;
809 csr_output_value = mepc;
810 csr_written_value = evaluate_csr_funct3_operation(decoder_funct3, csr_output_value, csr_input_value);
812 mepc = csr_written_value;
815 csr_output_value = mcause;
816 csr_written_value = evaluate_csr_funct3_operation(decoder_funct3, csr_output_value, csr_input_value);
818 mcause = csr_written_value;
821 csr_output_value = 0;
822 csr_output_value[11] = mip_meip;
823 csr_output_value[9] = mip_seip;
824 csr_output_value[8] = mip_ueip;
825 csr_output_value[7] = mip_mtip;
826 csr_output_value[5] = mip_stip;
827 csr_output_value[4] = mip_utip;
828 csr_output_value[3] = mip_msip;
829 csr_output_value[1] = mip_ssip;
830 csr_output_value[0] = mip_usip;
834 write_register(decoder_rd, csr_output_value);
836 else if((decode_action & (`decode_action_fence | `decode_action_fence_i | `decode_action_store | `decode_action_branch)) != 0) begin