1 ---------------------------------------------------------------------------------
4 -- Filename: core_ctrl.vhd
5 -- Description: the control unit for the TUD MB-Lite implementation
7 -- Author: Huib Lincklaen Arriens
8 -- Delft University of Technology
9 -- Faculty EEMCS, Department ME&CE, Circuits and Systems
10 -- Date: December, 2010
11 -- Modified: September, 2012: interrupt handling corrected to let
12 -- a pending branch be taken first
13 -- (with thanks to Matthis Meier, TU Dortmund,
14 -- for detecting this errror).
17 --------------------------------------------------------------------------------
21 USE IEEE.std_logic_1164.all;
24 --------------------------------------------------------------------------------
26 --------------------------------------------------------------------------------
28 COMPATIBILITY_MODE_g : BOOLEAN := FALSE
33 halt_i : IN STD_LOGIC;
34 bad_op_i : IN STD_LOGIC;
36 trace_i : IN STD_LOGIC;
37 trace_kick_i : IN STD_LOGIC;
38 core_clken_o : OUT STD_LOGIC;
40 imem_addr_o : OUT STD_LOGIC_VECTOR (31 DOWNTO 0);
41 imem_clken_o : OUT STD_LOGIC;
42 pc_ctrl_o : OUT STD_LOGIC;
43 -- fetch to decode pipeline registers
44 IF2ID_REG_i : IN IF2ID_Type;
45 IF2ID_REG_o : OUT IF2ID_Type;
46 -- decode to exeq pipeline registers
47 ID2EX_REG_i : IN ID2EX_Type;
48 ID2EX_REG_o : OUT ID2EX_Type;
50 gprf_clken_o : OUT STD_LOGIC;
51 -- exeq to fetch feedback registers
52 EX2IF_REG_i : IN EX2IF_Type;
53 EX2IF_REG_o : OUT EX2IF_Type;
54 -- exeq to core (halting)
55 exeq_halt_i : IN STD_LOGIC;
56 -- exeq to mem pipeline registers
57 EX2MEM_REG_i : IN EX2MEM_Type;
58 EX2MEM_REG_o : OUT EX2MEM_Type;
59 -- mem pipeline register
60 MEM_REG_i : IN MEM_REG_Type;
61 MEM_REG_o : OUT MEM_REG_Type;
63 ID2CTRL_i : IN ID2CTRL_Type;
64 INT_CTRL_o : OUT INT_CTRL_Type;
66 EX_WRB_i : IN WRB_Type;
67 EX_WRB_o : OUT WRB_Type;
69 HAZARD_WRB_i : IN HAZARD_WRB_Type;
70 HAZARD_WRB_o : OUT HAZARD_WRB_Type;
71 -- for handling the 'IMM' instruction
72 IMM_LOCK_i : IN IMM_LOCK_Type;
73 IMM_LOCK_o : OUT IMM_LOCK_Type;
74 -- for handling the Machine Status Register
78 MEM2CTRL_i : IN MEM2CTRL_Type
82 --------------------------------------------------------------------------------
83 ARCHITECTURE rtl OF core_ctrl IS
84 --------------------------------------------------------------------------------
86 SIGNAL rst_r : STD_LOGIC;
87 SIGNAL reset_s : STD_LOGIC;
88 SIGNAL core_clken_s : STD_LOGIC;
90 SIGNAL ID2EX_REG_r : ID2EX_Type;
91 SIGNAL EX2IF_REG_r : EX2IF_Type;
92 SIGNAL IMM_LOCK_r : IMM_LOCK_Type;
93 SIGNAL HAZARD_WRB_r : HAZARD_WRB_Type;
94 SIGNAL delayBit_r : STD_LOGIC;
95 SIGNAL clken_s : STD_LOGIC;
96 SIGNAL clken_pipe_s : STD_LOGIC;
97 SIGNAL flush_ID2EX_s : STD_LOGIC;
98 SIGNAL flush_ID2EX_r : STD_LOGIC;
99 SIGNAL flush_EX2MEM_s : STD_LOGIC;
101 SIGNAL setup_int_r : STD_LOGIC;
102 SIGNAL int_busy_r : STD_LOGIC;
106 -- static connections
107 reset_s <= rst_i OR rst_r;
108 pc_ctrl_o <= NOT rst_r;
109 imem_addr_o <= IF2ID_REG_i.program_counter;
111 -- Reset_s is 1 when rst_i is one and then gets deactivated
112 core_clken_s <= reset_s OR ((NOT bad_op_i) AND (((NOT trace_i) AND (NOT exeq_halt_i)) OR trace_kick_i));
113 core_clken_o <= core_clken_s;
114 -- clock/wait control lines
115 clken_s <= MEM2CTRL_i.clken OR rst_i;
116 clken_pipe_s <= clken_s AND (NOT HAZARD_WRB_i.hazard);
117 imem_clken_o <= clken_pipe_s;
118 gprf_clken_o <= clken_s;
119 -- signals for clearing the ID2EX and EX2MEM registers during branches
120 flush_ID2EX_s <= ((EX2IF_REG_i.take_branch AND (NOT delayBit_r)) OR EX2IF_REG_r.take_branch) WHEN COMPATIBILITY_MODE_g = TRUE
121 ELSE (EX2IF_REG_i.take_branch OR EX2IF_REG_r.take_branch);
122 flush_EX2MEM_s <= HAZARD_WRB_i.hazard;
123 -- outputs that need to be readable too, so needing shadowing signals
124 ID2EX_REG_o <= ID2EX_REG_r;
125 EX2IF_REG_o <= EX2IF_REG_r;
126 IMM_LOCK_o <= IMM_LOCK_r;
127 HAZARD_WRB_o <= HAZARD_WRB_r;
129 INT_CTRL_o.setup_int <= setup_int_r;
130 INT_CTRL_o.rti_target <= ID2EX_REG_r.program_counter;
131 INT_CTRL_o.int_busy <= int_busy_r;
134 PROCESS ( clk_i, rst_i, halt_i, core_clken_s,
135 -- complete sensitivity list for synthesizer
136 reset_s, MEM2CTRL_i, clken_pipe_s, IF2ID_REG_i,
137 flush_ID2EX_s, flush_EX2MEM_s, HAZARD_WRB_i,
138 MEM_REG_i, ID2CTRL_i, int_i, MSR_i,
139 int_busy_r, IMM_LOCK_i, ID2EX_REG_i, ID2EX_REG_r,
140 EX2IF_REG_i, EX_WRB_i, EX2MEM_REG_i )
142 -- some local procedures
143 PROCEDURE lp_rst_IF2ID_REG IS
145 IF2ID_REG_o.program_counter <= (OTHERS => '0');
148 PROCEDURE lp_rst_ID2EX_REG IS
150 -- reset and handle ID2EX_REG_r.program_counter separately,
151 -- since it will be needed during interrupt setup
152 ID2EX_REG_r.rdix_rA <= (OTHERS => '0');
153 ID2EX_REG_r.rdix_rB <= (OTHERS => '0');
154 ID2EX_REG_r.curr_rD <= (OTHERS => '0');
155 ID2EX_REG_r.alu_Action <= A_NOP;
156 ID2EX_REG_r.alu_Op1 <= ALU_IN_ZERO;
157 ID2EX_REG_r.alu_Op2 <= ALU_IN_IMM;
158 ID2EX_REG_r.alu_Cin <= CIN_ZERO;
159 ID2EX_REG_r.IMM16 <= (OTHERS => '0');
160 ID2EX_REG_r.IMM_Lock <= '0';
161 ID2EX_REG_r.msr_Action <= KEEP_CARRY;
162 ID2EX_REG_r.branch_Action <= NO_BR;
163 ID2EX_REG_r.mem_Action <= NO_MEM;
164 ID2EX_REG_r.transfer_Size <= WORD;
165 ID2EX_REG_r.wrb_Action <= NO_WRB;
168 PROCEDURE lp_rst_EX2IF_REG IS
170 EX2IF_REG_r.take_branch <= '0';
171 EX2IF_REG_r.branch_target <= (OTHERS => '0');
174 PROCEDURE lp_rst_EX2MEM_REG IS
176 EX2MEM_REG_o.mem_Action <= NO_MEM;
177 EX2MEM_REG_o.wrb_Action <= NO_WRB;
178 EX2MEM_REG_o.exeq_result <= (OTHERS => '0');
179 EX2MEM_REG_o.data_rD <= (OTHERS => '0');
180 EX2MEM_REG_o.byte_Enable <= (OTHERS => '0');
181 EX2MEM_REG_o.wrix_rD <= (OTHERS => '0');
184 PROCEDURE lp_rst_IMM_LOCK IS
186 IMM_LOCK_r.locked <= '0';
187 IMM_LOCK_r.IMM_hi16 <= (OTHERS => '0');
190 PROCEDURE lp_rst_MSR IS
196 PROCEDURE lp_rst_EX_WRB IS
198 EX_WRB_o.wrb_Action <= NO_WRB;
199 EX_WRB_o.wrix_rD <= (OTHERS => '0');
200 EX_WRB_o.data_rD <= (OTHERS => '0');
203 PROCEDURE lp_rst_HAZARD_WRB IS
205 HAZARD_WRB_r.hazard <= '0';
206 HAZARD_WRB_r.save_rX <= NO_SAVE;
207 HAZARD_WRB_r.data_rX <= (OTHERS => '0');
208 HAZARD_WRB_r.data_rD <= (OTHERS => '0');
211 PROCEDURE lp_rst_MEM_REG IS
213 MEM_REG_o.wrb_Action <= NO_WRB;
214 MEM_REG_o.exeq_result <= (OTHERS => '0');
215 MEM_REG_o.byte_Enable <= (OTHERS => '0');
216 MEM_REG_o.wrix_rD <= (OTHERS => '0');
221 IF (RISING_EDGE (clk_i) AND (MEM2CTRL_i.clken = '1')) AND halt_i = '0' AND
222 core_clken_s = '1' THEN
225 IF (reset_s = '1') THEN -- synchronous reset ...
226 lp_rst_IF2ID_REG; -- ... so lasts at least one clock_cycle
231 IF (COMPATIBILITY_MODE_g = TRUE) THEN
235 flush_ID2EX_r <= '0';
238 ID2EX_REG_r.program_counter <= (OTHERS => '0');
240 IF (clken_pipe_s = '1') THEN
241 IF2ID_REG_o <= IF2ID_REG_i;
243 flush_ID2EX_r <= flush_ID2EX_s;
244 HAZARD_WRB_r <= HAZARD_WRB_i;
245 MEM_REG_o <= MEM_REG_i;
246 int_busy_r <= ID2CTRL_i.int_busy;
248 -- decode-to-exeq unit registers
249 IF ((reset_s = '1') OR (flush_ID2EX_s = '1')) THEN
252 IF (COMPATIBILITY_MODE_g = TRUE) THEN
255 -- check for the need and possibility to handle active interrupt requests
256 ELSIF (((int_i = '1') OR (MEM2CTRL_i.int = '1')) AND (MSR_i.IE = '1') AND
257 (ID2CTRL_i.int_busy = '0') AND (int_busy_r = '0') AND
258 -- pending branch should be taken before interrupt can be executed
259 -- dectected by Matthis Meier, TU Dortmund (Sept 2012)
260 (EX2IF_REG_i.take_branch = '0') AND
261 (EX2IF_REG_r.take_branch = '0') AND -- it is still pending a cycle after branching
262 (IMM_LOCK_i.locked = '0') AND
263 (HAZARD_WRB_i.hazard = '0')) THEN
265 ID2EX_REG_r.program_counter <= ID2EX_REG_i.program_counter;
267 ELSIF (clken_pipe_s = '1') THEN
269 ID2EX_REG_r <= ID2EX_REG_i;
270 IF (COMPATIBILITY_MODE_g = TRUE) THEN
271 delayBit_r <= ID2CTRL_i.delayBit;
274 -- exeq-to-mem unit registers
275 IF ((reset_s = '1') OR (flush_EX2MEM_s = '1')) THEN
281 IF (clken_pipe_s = '1') THEN
282 EX2IF_REG_r <= EX2IF_REG_i;
283 EX_WRB_o <= EX_WRB_i;
285 IF (clken_s = '1') THEN
286 -- next test to prevent a flush from disrupting
287 -- the write-back pipeline
288 IF (flush_ID2EX_r = '0') THEN
289 EX2MEM_REG_o <= EX2MEM_REG_i;
291 IMM_LOCK_r <= IMM_LOCK_i;
295 END IF; -- rising edge clk_i ...
296 END PROCESS regd_proc;
298 END ARCHITECTURE rtl;