diff --git a/insns/insn_bltu.py b/insns/insn_bltu.py
index 5f44e4c..58d60d2 100644
--- a/insns/insn_bltu.py
+++ b/insns/insn_bltu.py
@@ -1,88 +1,22 @@
-from nmigen import *
+from insn_SB_type import *
 
-class rvfi_insn_bltu(Elaboratable):
+class rvfi_insn_bltu(rvfi_insn_SB_type):
     def __init__(self, RISCV_FORMAL_ILEN=32, RISCV_FORMAL_XLEN=32):
-        self.RISCV_FORMAL_ILEN = RISCV_FORMAL_ILEN
-        self.RISCV_FORMAL_XLEN = RISCV_FORMAL_XLEN
-        self.rvfi_valid = Signal(1)
-        self.rvfi_insn = Signal(self.RISCV_FORMAL_ILEN)
-        self.rvfi_pc_rdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.rvfi_rs1_rdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.rvfi_rs2_rdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.rvfi_mem_rdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.spec_valid = Signal(1)
-        self.spec_trap = Signal(1)
-        self.spec_rs1_addr = Signal(5)
-        self.spec_rs2_addr = Signal(5)
-        self.spec_rd_addr = Signal(5)
-        self.spec_rd_wdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.spec_pc_wdata = Signal(self.RISCV_FORMAL_XLEN)
-        self.spec_mem_addr = Signal(self.RISCV_FORMAL_XLEN)
-        self.spec_mem_rmask = Signal(int(self.RISCV_FORMAL_XLEN // 8))
-        self.spec_mem_wmask = Signal(int(self.RISCV_FORMAL_XLEN // 8))
-        self.spec_mem_wdata = Signal(self.RISCV_FORMAL_XLEN)
+        super(rvfi_insn_bltu, self).__init__(RISCV_FORMAL_ILEN, RISCV_FORMAL_XLEN)
     def ports(self):
-        input_ports = [
-            self.rvfi_valid,
-            self.rvfi_insn,
-            self.rvfi_pc_rdata,
-            self.rvfi_rs1_rdata,
-            self.rvfi_rs2_rdata,
-            self.rvfi_mem_rdata
-        ]
-        output_ports = [
-            self.spec_valid,
-            self.spec_trap,
-            self.spec_rs1_addr,
-            self.spec_rs2_addr,
-            self.spec_rd_addr,
-            self.spec_rd_wdata,
-            self.spec_pc_wdata,
-            self.spec_mem_addr,
-            self.spec_mem_rmask,
-            self.spec_mem_wmask,
-            self.spec_mem_wdata
-        ]
-        return input_ports + output_ports
+        return super(rvfi_insn_bltu, self).ports()
     def elaborate(self, platform):
-        m = Module()
-
-        # SB-type instruction format
-        insn_padding = Signal(self.RISCV_FORMAL_ILEN)
-        m.d.comb += insn_padding.eq(self.rvfi_insn >> 32)
-        insn_imm = Signal(self.RISCV_FORMAL_XLEN)
-        m.d.comb += insn_imm.eq(Value.as_signed(Cat(self.rvfi_insn[8:12], self.rvfi_insn[25:31], self.rvfi_insn[7], self.rvfi_insn[31]) << 1))
-        insn_rs2 = Signal(5)
-        m.d.comb += insn_rs2.eq(self.rvfi_insn[20:25])
-        insn_rs1 = Signal(5)
-        m.d.comb += insn_rs1.eq(self.rvfi_insn[15:20])
-        insn_funct3 = Signal(3)
-        m.d.comb += insn_funct3.eq(self.rvfi_insn[12:15])
-        insn_opcode = Signal(7)
-        m.d.comb += insn_opcode.eq(self.rvfi_insn[:7])
-
-        misa_ok = Signal(1)
-        m.d.comb += misa_ok.eq(1)
-        ialign16 = Signal(1)
-        m.d.comb += ialign16.eq(0)
+        m = super(rvfi_insn_bltu, self).elaborate(platform)
 
         # BLTU instruction
         cond = Signal(1)
         m.d.comb += cond.eq(self.rvfi_rs1_rdata < self.rvfi_rs2_rdata)
         next_pc = Signal(self.RISCV_FORMAL_XLEN)
-        m.d.comb += next_pc.eq(Mux(cond, self.rvfi_pc_rdata + insn_imm, self.rvfi_pc_rdata + 4))
-        m.d.comb += self.spec_valid.eq(self.rvfi_valid & (~insn_padding) & (insn_funct3 == 0b110) & (insn_opcode == 0b1100011))
-        m.d.comb += self.spec_rs1_addr.eq(insn_rs1)
-        m.d.comb += self.spec_rs2_addr.eq(insn_rs2)
+        m.d.comb += next_pc.eq(Mux(cond, self.rvfi_pc_rdata + self.insn_imm, self.rvfi_pc_rdata + 4))
+        m.d.comb += self.spec_valid.eq(self.rvfi_valid & (~self.insn_padding) & (self.insn_funct3 == 0b110) & (self.insn_opcode == 0b1100011))
+        m.d.comb += self.spec_rs1_addr.eq(self.insn_rs1)
+        m.d.comb += self.spec_rs2_addr.eq(self.insn_rs2)
         m.d.comb += self.spec_pc_wdata.eq(next_pc)
-        m.d.comb += self.spec_trap.eq(Mux(ialign16, next_pc[0] != 0, next_pc[:2] != 0) | ~misa_ok)
-
-        # default assignments
-        m.d.comb += self.spec_rd_addr.eq(0)
-        m.d.comb += self.spec_rd_wdata.eq(0)
-        m.d.comb += self.spec_mem_addr.eq(0)
-        m.d.comb += self.spec_mem_rmask.eq(0)
-        m.d.comb += self.spec_mem_wmask.eq(0)
-        m.d.comb += self.spec_mem_wdata.eq(0)
+        m.d.comb += self.spec_trap.eq(Mux(self.ialign16, next_pc[0] != 0, next_pc[:2] != 0) | ~self.misa_ok)
 
         return m