基于RV32I指令集的单周期CPU，实现了部分指令集，包含五级流水线实现；并在Genesys2上验证并部署（双向）流水灯。
./rtl下为RTL源码，其中./rtl/core/pipeline包含使用五级流水线实现所需的模块./test/mem下为仿真测试所需文件，其中.s为测试的汇编程序（包括可部署至FPGA及便于仿真的简化程序），.mem为对应的机器码；./test/test.sh包含使用iverilog编译、仿真、查看波形等简单命令
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使用iverilog进行仿真，通过
-s <example_name>指定所仿真的示例，从而选择不同的.mem指令至imem中。具体选项参见下方示例或./test/test.sh。所生成的.vvp及.fst波形文件位于./test/simple或./test/pipeline（若使用五级流水线实现）下。-
RV32I指令测试仿真程序
bash test/test.sh -s SIM_VALUE25
若成功运行且RTL正确，将输出仿真正确信息，仿真的最后
dmem地址100处将写入25。 -
单向流水灯仿真程序
bash test/test.sh -s SIM_ROTATING_LEDS
t4寄存器将等时间间隔地（对应实际间隔0.5s）从32'h1、32'h2左移至32'h80，再置32'h01，以此往复，从而对应实际8个LED的单向依次闪烁。 -
双向流水灯仿真程序
bash test/test.sh -s SIM_DB_ROTATING_LEDS
t4寄存器将等时间间隔地（对应实际间隔0.5s）从32'h1、32'h2左移至32'h80，再右移至32'h01，以此往复，从而对应实际8个LED的双向依次闪烁。 -
五级流水线部署实现。通过
-p选项编译五级流水线实现的CPU：bash test/test.sh -s SIM_ROTATING_LEDS -p # Also works bash test/test.sh -p -s SIM_VALUE25
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使用Vivado进行上板部署：需例化Clock Wizard IP，并根据FPGA实际时钟（单端/差分）修改例化部分的RTL代码。在Genesys2开发板上，需例化一双端差分转单端、无复位、100MHz输出的Clock Wizard IP。
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单向流水灯。若在Vivado上部署此工程，则在
./rtl/core/config.vh下开启此宏定义：`define USE_ROTATING_LEDS_EXAMPLE部署在Genesys2的现象：8个LED将从LED0~LED7间隔~0.5s依次闪烁。
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双向流水灯。若在Vivado上部署此工程，则在
./rtl/core/config.vh下开启此宏定义，同时注释前一宏定义：// `define USE_ROTATING_LEDS_EXAMPLE // This macro definition will mask the next one. `define USE_DOUBLE_SIDE_ROTATING_LEDS_EXAMPLE
部署在Genesys2的现象：8个LED将从LED~LED7~LED0间隔~0.5s双向依次闪烁。
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五级流水线部署实现。若在Vivado上实现五级流水线部署，则在
./rtl/core/config.vh下开启此宏定义：`define USE_PIPELINE
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所实现的RV32I指令包括：
Instruction opcode funct3 funct7 ADD 7'b0110011 3'b000 0 SUB 7'b0110011 3'b000 7'b0100000 AND 7'b0110011 3'b111 0 XOR 7'b0110011 3'b101 0 OR 7'b0110011 3'b110 0 SLT 7'b0110011 3'b010 0 SLL 7'b0110011 3'b011 0 SRL 7'b0110011 3'b100 0 ADDI 7'b0010011 3'b000 immediate ANDI 7'b0010011 3'b111 immediate XORI 7'b0010011 3'b101 immediate ORI 7'b0010011 3'b110 immediate SLTI 7'b0010011 3'b010 immediate SLLI 7'b0010011 3'b011 immediate SRLI 7'b0010011 3'b100 immediate BEQ 7'b1100011 3'b000 immediate LW 7'b0000011 3'b010 immediate SW 7'b0100011 3'b010 immediate JAL 7'b1101111 immediate immediate -
RV32I指令测试：测试所设计的所有指令，最终将25写入
dmem地址100处# RISC-V Assembly Description Address Machine Code main: addi x2, x0, 5 # x2 = 5 00 0x00500113 addi x3, x0, 12 # x3 = 12 04 0x00C00193 addi x7, x3, -9 # x7 = (12 - 9) = 3 08 0xFF718393 or x4, x7, x2 # x4 = (3 OR 5) = 7 0C 0x0023E233 and x5, x3, x4 # x5 = (12 AND 7) = 4 10 0x0041F2B3 add x5, x5, x4 # x5 = (4 + 7) = 11 14 0x004282B3 beq x5, x7, end # shouldn't be taken 18 0x02728863 slt x4, x3, x4 # x4 = (12 < 7) = 0 1C 0x0041A233 beq x4, x0, around # should be taken 20 0x00020463 addi x5, x0, 0 # shouldn't happen 24 0x00000293 around: slt x4, x7, x2 # x4 = (3 < 5) = 1 28 0x0023A233 add x7, x4, x5 # x7 = (1 + 11) = 12 2C 0x005203B3 sub x7, x7, x2 # x7 = (12 - 5) = 7 30 0x402383B3 sw x7, 84(x3) # [96] = 7 34 0x0471AA23 lw x2, 96(x0) # x2 = [96] = 7 38 0x06002103 add x9, x2, x5 # x9 = (7 + 11) = 18 3C 0x005104B3 jal x3, end # jump to end, x3 = 0x44 40 0x008001EF addi x2, x0, 1 # shouldn't happen 44 0x00100113 end: add x2, x2, x9 # x2 = (7 + 18) = 25 48 0x00910133 sw x2, 0x20(x3) # mem[100] = 25 4C 0x0221A023 done: beq x2, x2, done # infinite loop 50 0x00210063
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单向流水灯。板上时钟频率100MHz，借助
t5寄存器及循环计数，达到$$ 100\text{M}/(2047\times 8192\times 3)\approx 2\text{Hz} $$ 分频，实现间隔~0.5秒闪烁效果。在Genesys2上，
t4寄存器低八位对应8个LED。# RISC-V Assembly Description Address Machine Code init: addi t5, x0, 2047 # count_max, t5 = 2047 00 0x7FF00F13 add t5, t5, t5 # count_max, t5 = 2047*2 04 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*4 08 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*8 0C 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*16 10 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*32 14 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*64 18 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*128 1C 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*256 20 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*512 24 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*1024 28 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*2048 2C 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*4096 30 0x01EF0F33 add t5, t5, t5 # count_max, t5 = 2047*8192 34 0x01EF0F33 addi t6, x0, 256 # led_max, t6 = 256 38 0x10000F93 addi t4, x0, 1 # init led value, t4 = 1 3C 0x00100E93 clean_cnt: addi t3, x0, 0 # clear count(t3). 40 0x00000E13 count: addi t3, t3, 1 # count++ 44 0x001E0E13 beq t3, t5, mov_led # if count==max, jump mov_led 48 0x01EE0463 jal count # 4C 0xFF9FF06F mov_led: add t4, t4, t4 # led << 1. 50 0x01DE8EB3 beq t4, t6, clean_led # 54 0xFFFE84E3 jal clean_cnt # 58 0xFE9FF06F
其中，各寄存器含义如下表所列：
Register Address Meaning t35'b11100 Counter of t5t45'b11101 LED result t55'b11110 0.5s time count t65'b11111 Led max value -
双向流水灯。在上述示例基础上实现双向闪烁，主要利用左移（
SLLI）、右移（SRLI）。# RISC-V Assembly Description Address Machine Code init: addi t5, x0, 2047 # count_max, t5 = 2047 00 0x7FF00F13 addi t3, x0, 13 # loop_cnt = 13 04 0x00D00E13 addi x1, x0, 0 # x1 = 0 08 0x00000293 init_loop: addi x1, x1, 1 # x1 += 1 0C 0x00128293 slli t5, t5, 1 # t5 << 1 10 0x001F3F13 beq x1, t3, start # if x1 == t3, jump start 14 0x005E0463 jal init_loop # 18 0xFF5FF06F start: addi t6, x0, 256 # led_max = 256 1C 0x10000F93 addi x1, x0, 1C # x1 = 1 20 0x00100093 new_cycle: addi t4, x0, 1 # init led value, t4 = 1 24 0x00100E93 inc_clr_cnt:addi t3, x0, 0 # clear count(t3) 28 0x00000E13 inc_count: addi t3, t3, 1 # count++ 2C 0x001E0E13 beq t3, t5, inc_led # if count == max, jump inc_led 30 0x01EE0463 jal inc_count # 34 0xFF9FF06F inc_led: slli t4, t4, 1 # led << 1 38 0x001EBE93 beq t4, t6, jump256 # if led = 256, jump jump256 3C 0x01FE8C63 jal inc_clr_cnt # 40 0xFE9FF06F dec_clr_cnt:addi t3, x0, 0 # clear count(t3) 44 0x00000E13 dec_count: addi t3, t3, 1 # count++ 48 0x001E0E13 beq t3, t5, dec_led # if count == max, jump dec_led 4C 0x01EE0663 jal dec_count # 50 0xFF9FF06F jump256: srli t4, t4, 1 # led >> 1 = 128 54 0x001ECE93 dec_led: srli t4, t4, 1 # led >> 1 58 0x001ECE93 beq t4, x1, new_cycle # if led = 1, jump new_cycle 5C 0xFC1E84E3 jal dec_clr_cnt # 60 0xFE5FF06F
其中，各寄存器含义如下表所列：
Register Address Meaning x15'b00001 Temporary register t35'b11100 Counter of t5t45'b11101 LED result t55'b11110 0.5s time count t65'b11111 LED max value