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5 -- Description: the Memory (MEM) control unit for
6 -- the TUD MB-Lite implementation
8 -- Author: Huib Lincklaen Arriens
9 -- Delft University of Technology
10 -- Faculty EEMCS, Department ME&CE, Circuits and Systems
11 -- Date: October, 2010
13 -- Modified: December, 2010: handle S_FSL Data Input (Huib)
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18 USE IEEE.std_logic_1164.all;
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26 EX2MEM_i : IN EX2MEM_Type;
28 DMEMB_i : IN DMEMB2CORE_Type;
29 DMEMB_o : OUT CORE2DMEMB_Type;
31 MEM_REG_i : IN MEM_REG_Type;
32 MEM_REG_o : OUT MEM_REG_Type;
34 MEM_WRB_o : OUT WRB_Type;
35 MEM2CTRL_o : OUT MEM2CTRL_Type
39 --------------------------------------------------------------------------------
40 ARCHITECTURE rtl OF mem IS
41 --------------------------------------------------------------------------------
45 -- writeback in case of reads from the data memory bus:
46 -- delay wrb-ctrl signals (see core_ctrl) to stay in sync
47 -- with synchronous dmem data output
48 -- Following are only the unconditional pass-through signals. More are in the p_mem process.
49 MEM_REG_o.wrb_Action <= EX2MEM_i.wrb_Action;
50 MEM_REG_o.exeq_result <= EX2MEM_i.exeq_result;
51 MEM_REG_o.byte_Enable <= EX2MEM_i.byte_Enable;
52 MEM_REG_o.wrix_rD <= EX2MEM_i.wrix_rD;
54 MEM_WRB_o.wrb_Action <= MEM_REG_i.wrb_Action;
55 MEM_WRB_o.wrix_rD <= MEM_REG_i.wrix_rD;
56 -- also signal 'slow memory decices' and interrupts from devices
57 MEM2CTRL_o.clken <= DMEMB_i.clken;
58 MEM2CTRL_o.int <= DMEMB_i.int;
59 -- pass byte_select signal (NOTE: BIG ENDIAN)
60 DMEMB_o.bSel <= EX2MEM_i.byte_Enable;
63 PROCESS (EX2MEM_i, DMEMB_i, MEM_REG_i)
64 VARIABLE exeq_data_v : STD_LOGIC_VECTOR (31 DOWNTO 0);
65 VARIABLE dmem_data_v : STD_LOGIC_VECTOR (31 DOWNTO 0);
69 -- always align Big Endian input data from memory(-bus)
70 CASE MEM_REG_i.byte_Enable IS
71 WHEN "1000" => dmem_data_v := C_24_ZEROS & DMEMB_i.data(31 DOWNTO 24);
72 WHEN "0100" => dmem_data_v := C_24_ZEROS & DMEMB_i.data(23 DOWNTO 16);
73 WHEN "0010" => dmem_data_v := C_24_ZEROS & DMEMB_i.data(15 DOWNTO 8);
74 WHEN "0001" => dmem_data_v := C_24_ZEROS & DMEMB_i.data( 7 DOWNTO 0);
75 WHEN "1100" => dmem_data_v := C_16_ZEROS & DMEMB_i.data(31 DOWNTO 16);
76 WHEN "0011" => dmem_data_v := C_16_ZEROS & DMEMB_i.data(15 DOWNTO 0);
77 WHEN OTHERS => dmem_data_v := DMEMB_i.data;
81 CASE EX2MEM_i.mem_Action IS
84 -- write (or forward) to data memory bus
85 DMEMB_o.addr <= EX2MEM_i.exeq_result;
88 -- Note: use MEM_REG_i here, since MEM_WRB_o (output) cannot be read
89 IF ((MEM_REG_i.wrb_Action /= NO_WRB) AND
90 (EX2MEM_i.wrix_rD = MEM_REG_i.wrix_rD)) THEN
91 CASE MEM_REG_i.wrb_Action IS
93 -- forward exeq output, to handle e.g. add rD,rA,xx; sw rD,mem[y]; ...
94 exeq_data_v := MEM_REG_i.exeq_result;
96 -- forward mem_data just read, to handle e.g. lhu rD,mem[x]; sh rD,mem[y]; ...
97 exeq_data_v := dmem_data_v;
100 exeq_data_v := EX2MEM_i.data_rD;
102 -- output data will be in Big Endian format
103 CASE EX2MEM_i.byte_Enable IS
104 WHEN "1000" => DMEMB_o.data <= exeq_data_v( 7 DOWNTO 0) & C_24_ZEROS;
105 WHEN "0100" => DMEMB_o.data <= C_8_ZEROS & exeq_data_v( 7 DOWNTO 0) & C_16_ZEROS;
106 WHEN "0010" => DMEMB_o.data <= C_16_ZEROS & exeq_data_v( 7 DOWNTO 0) & C_8_ZEROS;
107 WHEN "0001" => DMEMB_o.data <= C_24_ZEROS & exeq_data_v( 7 DOWNTO 0);
108 WHEN "1100" => DMEMB_o.data <= exeq_data_v(15 DOWNTO 0) & C_16_ZEROS;
109 WHEN "0011" => DMEMB_o.data <= C_16_ZEROS & exeq_data_v(15 DOWNTO 0);
110 WHEN OTHERS => DMEMB_o.data <= exeq_data_v;
114 -- read from data memory bus
115 DMEMB_o.addr <= EX2MEM_i.exeq_result;
118 DMEMB_o.data <= EX2MEM_i.data_rD; -- (OTHERS => 'Z');
120 WHEN OTHERS => -- NO_MEM
121 DMEMB_o.addr <= C_32_ZEROS;
124 DMEMB_o.data <= EX2MEM_i.data_rD; -- (OTHERS => 'Z');
127 -- additional wrb signals
128 CASE MEM_REG_i.wrb_Action IS
129 WHEN WRB_MEM => MEM_WRB_o.data_rD <= dmem_data_v;
130 WHEN OTHERS => MEM_WRB_o.data_rD <= MEM_REG_i.exeq_result;
135 END ARCHITECTURE rtl;