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;
25 --------------------------------------------------------------------------------
27 --------------------------------------------------------------------------------
31 halt_i : IN STD_LOGIC;
34 imem_addr_o : OUT STD_LOGIC_VECTOR (31 DOWNTO 0);
35 imem_clken_o : OUT STD_LOGIC;
36 pc_ctrl_o : OUT STD_LOGIC;
37 -- fetch to decode pipeline registers
38 IF2ID_REG_i : IN IF2ID_Type;
39 IF2ID_REG_o : OUT IF2ID_Type;
40 -- decode to exeq pipeline registers
41 ID2EX_REG_i : IN ID2EX_Type;
42 ID2EX_REG_o : OUT ID2EX_Type;
44 gprf_clken_o : OUT STD_LOGIC;
45 -- exeq to fetch feedback registers
46 EX2IF_REG_i : IN EX2IF_Type;
47 EX2IF_REG_o : OUT EX2IF_Type;
48 -- exeq to mem pipeline registers
49 EX2MEM_REG_i : IN EX2MEM_Type;
50 EX2MEM_REG_o : OUT EX2MEM_Type;
51 -- mem pipeline register
52 MEM_REG_i : IN MEM_REG_Type;
53 MEM_REG_o : OUT MEM_REG_Type;
54 -- FSL to mem data delay register(s)
55 FSL_S2MEM_REG_i : IN FSL_S2MEM_Type;
56 FSL_S2MEM_REG_o : OUT FSL_S2MEM_Type;
58 ID2CTRL_i : IN ID2CTRL_Type;
59 INT_CTRL_o : OUT INT_CTRL_Type;
61 EX_WRB_i : IN WRB_Type;
62 EX_WRB_o : OUT WRB_Type;
64 HAZARD_WRB_i : IN HAZARD_WRB_Type;
65 HAZARD_WRB_o : OUT HAZARD_WRB_Type;
66 -- for handling the 'IMM' instruction
67 IMM_LOCK_i : IN IMM_LOCK_Type;
68 IMM_LOCK_o : OUT IMM_LOCK_Type;
69 -- for handling the Machine Status Register
73 MEM2CTRL_i : IN MEM2CTRL_Type;
74 FSL_nStall_i : IN STD_LOGIC;
75 done_o : OUT STD_LOGIC
79 --------------------------------------------------------------------------------
80 ARCHITECTURE rtl OF core_ctrl IS
81 --------------------------------------------------------------------------------
83 SIGNAL rst_r : STD_LOGIC;
84 SIGNAL reset_s : STD_LOGIC;
86 SIGNAL ID2EX_REG_r : ID2EX_Type;
87 SIGNAL EX2IF_REG_r : EX2IF_Type;
88 SIGNAL delayBit_r : STD_LOGIC;
89 SIGNAL delayBit_2r : STD_LOGIC;
90 SIGNAL IMM_LOCK_r : IMM_LOCK_Type;
91 SIGNAL HAZARD_WRB_r : HAZARD_WRB_Type;
93 SIGNAL clken_s : STD_LOGIC;
94 SIGNAL clken_pipe_s : STD_LOGIC;
95 SIGNAL flush_ID2EX_s : STD_LOGIC;
96 SIGNAL flush_ID2EX_r : STD_LOGIC;
97 SIGNAL flush_EX2MEM_s : STD_LOGIC;
99 SIGNAL setup_int_r : STD_LOGIC;
100 SIGNAL int_busy_r : STD_LOGIC;
102 SIGNAL S_Data_r : STD_LOGIC_VECTOR (31 DOWNTO 0);
103 SIGNAL S_Data_2r : STD_LOGIC_VECTOR (31 DOWNTO 0);
108 -- static connections
109 reset_s <= rst_i OR rst_r;
110 pc_ctrl_o <= NOT rst_r;
111 imem_addr_o <= IF2ID_REG_i.program_counter;
112 -- clock/wait control lines
113 clken_s <= (MEM2CTRL_i.clken AND FSL_nStall_i) OR rst_i;
114 clken_pipe_s <= clken_s AND (NOT HAZARD_WRB_i.hazard);
115 imem_clken_o <= clken_pipe_s;
116 gprf_clken_o <= clken_s;
117 -- signals for clearing the ID2EX and EX2MEM registers during branches
118 flush_ID2EX_s <= EX2IF_REG_r.take_branch;
119 flush_EX2MEM_s <= (flush_ID2EX_s AND (NOT delayBit_2r)) OR HAZARD_WRB_i.hazard;
120 -- outputs that need to be readable too, so needing shadowing signals
121 ID2EX_REG_o <= ID2EX_REG_r;
122 EX2IF_REG_o <= EX2IF_REG_r;
123 IMM_LOCK_o <= IMM_LOCK_r;
124 HAZARD_WRB_o <= HAZARD_WRB_r;
126 INT_CTRL_o.setup_int <= setup_int_r;
127 INT_CTRL_o.rti_target <= ID2EX_REG_r.program_counter;
128 INT_CTRL_o.int_busy <= int_busy_r;
130 FSL_S2MEM_REG_o.S_Data <= S_Data_2r;
133 PROCESS ( clk_i, rst_i, halt_i,
134 -- complete sensitivity list for synthesizer
135 reset_s, MEM2CTRL_i, clken_pipe_s, IF2ID_REG_i,
136 flush_ID2EX_s, flush_EX2MEM_s, HAZARD_WRB_i,
137 MEM_REG_i, ID2CTRL_i, int_i, MSR_i,
138 int_busy_r, delayBit_r, IMM_LOCK_i, ID2EX_REG_i, ID2EX_REG_r,
139 EX2IF_REG_i, EX_WRB_i, S_Data_r, FSL_S2MEM_REG_i, EX2MEM_REG_i )
141 -- some local procedures
142 PROCEDURE lp_rst_IF2ID_REG IS
144 IF2ID_REG_o.program_counter <= (OTHERS => '0');
147 PROCEDURE lp_rst_ID2EX_REG IS
149 -- reset and handle ID2EX_REG_r.program_counter separately,
150 -- since it will be needed during interrupt setup
151 ID2EX_REG_r.rdix_rA <= (OTHERS => '0');
152 ID2EX_REG_r.rdix_rB <= (OTHERS => '0');
153 ID2EX_REG_r.curr_rD <= (OTHERS => '0');
154 ID2EX_REG_r.alu_Action <= A_NOP;
155 ID2EX_REG_r.alu_Op1 <= ALU_IN_ZERO;
156 ID2EX_REG_r.alu_Op2 <= ALU_IN_IMM;
157 ID2EX_REG_r.alu_Cin <= CIN_ZERO;
158 ID2EX_REG_r.IMM16 <= (OTHERS => '0');
159 ID2EX_REG_r.IMM_Lock <= '0';
160 ID2EX_REG_r.msr_Action <= KEEP_CARRY;
161 ID2EX_REG_r.branch_Action <= NO_BR;
162 ID2EX_REG_r.mem_Action <= NO_MEM;
163 ID2EX_REG_r.transfer_Size <= WORD;
164 ID2EX_REG_r.wrb_Action <= NO_WRB;
165 ID2EX_REG_r.FSL_Test <= '1';
166 ID2EX_REG_r.FSL_Non_blocking <= '1';
167 ID2EX_REG_r.FSL_Control <= '0';
168 ID2EX_REG_r.FSL_Atomic <= '0';
171 PROCEDURE lp_rst_EX2IF_REG IS
173 EX2IF_REG_r.take_branch <= '0';
174 EX2IF_REG_r.branch_target <= (OTHERS => '0');
177 PROCEDURE lp_rst_EX2MEM_REG IS
179 EX2MEM_REG_o.mem_Action <= NO_MEM;
180 EX2MEM_REG_o.wrb_Action <= NO_WRB;
181 EX2MEM_REG_o.exeq_result <= (OTHERS => '0');
182 EX2MEM_REG_o.data_rD <= (OTHERS => '0');
183 EX2MEM_REG_o.byte_Enable <= (OTHERS => '0');
184 EX2MEM_REG_o.wrix_rD <= (OTHERS => '0');
187 PROCEDURE lp_rst_FSL2MEM_REG IS
189 S_Data_r <= (OTHERS => '0');
190 S_Data_2r <= (OTHERS => '0');
193 PROCEDURE lp_rst_IMM_LOCK IS
195 IMM_LOCK_r.locked <= '0';
196 IMM_LOCK_r.IMM_hi16 <= (OTHERS => '0');
199 PROCEDURE lp_rst_MSR IS
206 PROCEDURE lp_rst_EX_WRB IS
208 EX_WRB_o.wrb_Action <= NO_WRB;
209 EX_WRB_o.wrix_rD <= (OTHERS => '0');
210 EX_WRB_o.data_rD <= (OTHERS => '0');
213 PROCEDURE lp_rst_HAZARD_WRB IS
215 HAZARD_WRB_r.hazard <= '0';
216 HAZARD_WRB_r.save_rX <= NO_SAVE;
217 HAZARD_WRB_r.data_rX <= (OTHERS => '0');
218 HAZARD_WRB_r.data_rD <= (OTHERS => '0');
221 PROCEDURE lp_rst_MEM_REG IS
223 MEM_REG_o.wrb_Action <= NO_WRB;
224 MEM_REG_o.exeq_result <= (OTHERS => '0');
225 MEM_REG_o.byte_Enable <= (OTHERS => '0');
226 MEM_REG_o.wrix_rD <= (OTHERS => '0');
230 IF (RISING_EDGE (clk_i) AND (MEM2CTRL_i.clken = '1')) AND halt_i = '0' THEN
232 IF (reset_s = '1') THEN -- synchronous reset ...
233 lp_rst_IF2ID_REG; -- ... so lasts at least one clock_cycle
239 flush_ID2EX_r <= '0';
243 ID2EX_REG_r.program_counter <= (OTHERS => '0');
245 IF (clken_pipe_s = '1') THEN
246 IF2ID_REG_o <= IF2ID_REG_i;
248 flush_ID2EX_r <= flush_ID2EX_s;
249 HAZARD_WRB_r <= HAZARD_WRB_i;
250 MEM_REG_o <= MEM_REG_i;
251 int_busy_r <= ID2CTRL_i.int_busy;
253 -- decode-to-exeq unit registers
254 IF ((reset_s = '1') OR (flush_ID2EX_s = '1')) THEN
257 -- check for the need and possibility to handle active interrupt requests
258 ELSIF (((int_i = '1') OR (MEM2CTRL_i.int = '1')) AND (MSR_i.IE = '1') AND
259 (ID2CTRL_i.int_busy = '0') AND (int_busy_r = '0') AND
260 -- pending branch should be taken before interrupt can be executed
261 -- dectected by Matthis Meier, TU Dortmund (Sept 2012)
262 (EX2IF_REG_i.take_branch = '0') AND
263 (delayBit_r = '0') AND
264 (IMM_LOCK_i.locked = '0') AND
265 (HAZARD_WRB_i.hazard = '0')) THEN
267 ID2EX_REG_r.program_counter <= ID2EX_REG_i.program_counter;
269 ELSIF (clken_pipe_s = '1') THEN
271 ID2EX_REG_r <= ID2EX_REG_i;
272 delayBit_r <= ID2CTRL_i.delayBit;
274 -- exeq-to-mem unit registers
275 IF ((reset_s = '1') OR (flush_EX2MEM_s = '1')) THEN
282 IF (clken_pipe_s = '1') THEN
283 EX2IF_REG_r <= EX2IF_REG_i;
284 delayBit_2r <= delayBit_r;
285 EX_WRB_o <= EX_WRB_i;
286 S_Data_2r <= S_Data_r;
287 S_Data_r <= FSL_S2MEM_REG_i.S_Data;
289 IF (clken_s = '1') THEN
290 -- next test to prevent a flush from disrupting
291 -- the write-back pipeline
292 IF (flush_ID2EX_r = '0') THEN
293 EX2MEM_REG_o <= EX2MEM_REG_i;
295 IMM_LOCK_r <= IMM_LOCK_i;
299 -- check on End-Of-Program viz. "bri 0x00"
300 -- use delayBit to distinguish between "bri" and "rtsd/rtid"
301 IF ((ID2EX_REG_r.branch_Action = BR) AND
302 (ID2EX_REG_r.alu_Op2 = ALU_IN_IMM) AND
303 (ID2EX_REG_r.IMM16 = C_16_ZEROS) AND
304 (delayBit_r = '0') AND (flush_EX2MEM_s = '0')) THEN
307 END IF; -- rising edge clk_i ...
308 END PROCESS regd_proc;
310 END ARCHITECTURE rtl;