diff --git a/emulator/src/foot-emulator.cpp b/emulator/src/foot-emulator.cpp
index 47d495d..b525582 100644
--- a/emulator/src/foot-emulator.cpp
+++ b/emulator/src/foot-emulator.cpp
@@ -27,6 +27,7 @@ uint16_t& Device::memory(uint16_t index)
 Emulator::Emulator() :
   memory{},
   registers{},
+  configuration(0),
   mapped_base(0)
 {}
 
@@ -349,7 +350,8 @@ void Emulator::DIVI()
   uint16_t  b = decode_operand((instruction & 0x0000FF00) >> 8);
   uint16_t& d = decode_operand((instruction & 0x00FF0000) >> 16);
 
-  d = uint32_t((int32_t(a) >> shift()) / int32_t(b));
+  // convert from unsigned to signed, then widen
+  d = uint32_t((int32_t(int16_t(a)) << shift()) / int32_t(int16_t(b)));
 }
 
 void Emulator::MODU()
@@ -358,7 +360,7 @@ void Emulator::MODU()
   uint16_t  b = decode_operand((instruction & 0x0000FF00) >> 8);
   uint16_t& d = decode_operand((instruction & 0x00FF0000) >> 16);
 
-  d = uint32_t((int32_t(a) >> shift()) / int32_t(b));
+  d = int16_t(a) % int16_t(b);
 }
 
 bool Emulator::repeats()
diff --git a/emulator/tests/CMakeLists.txt b/emulator/tests/CMakeLists.txt
index e674353..7960f0b 100644
--- a/emulator/tests/CMakeLists.txt
+++ b/emulator/tests/CMakeLists.txt
@@ -17,3 +17,9 @@ test(band-instruction)
 test(bxor-instruction)
 test(srsh-instruction)
 test(zlsh-instruction)
+test(clsh-instruction)
+test(addi-instruction)
+test(subt-instruction)
+test(mult-instruction)
+test(divi-instruction)
+test(modu-instruction)
diff --git a/emulator/tests/addi-instruction.cpp b/emulator/tests/addi-instruction.cpp
new file mode 100644
index 0000000..bff41f1
--- /dev/null
+++ b/emulator/tests/addi-instruction.cpp
@@ -0,0 +1,36 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x4567
+  //
+  // ADDI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00204567, 0x09200220 });
+    if (!check(0x4569, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x4567
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFFE (-2)
+  //
+  // ADDI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00204567, 0x0021FFFE, 0x09202120 });
+    if (!check(0x4565, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}
diff --git a/emulator/tests/clsh-instruction.cpp b/emulator/tests/clsh-instruction.cpp
new file mode 100644
index 0000000..c9c9db5
--- /dev/null
+++ b/emulator/tests/clsh-instruction.cpp
@@ -0,0 +1,19 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x4567
+  //
+  // CLSH
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00204567, 0x08200220 });
+    if (!check(0x159D, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}
diff --git a/emulator/tests/divi-instruction.cpp b/emulator/tests/divi-instruction.cpp
new file mode 100644
index 0000000..4df438c
--- /dev/null
+++ b/emulator/tests/divi-instruction.cpp
@@ -0,0 +1,75 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0005
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00200005, 0x0E200220 });
+    if (!check(0x0002, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0007
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFF9 (-7)
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200007, 0x0021FFF9, 0x0E202120 });
+    if (!check(0xFFFF, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0xFFF9 (-7)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFF9 (-7)
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x0020FFF9, 0x0021FFF9, 0x0E202120 });
+    if (!check(0x1, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0002 (1)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0x0001 (0.5)
+  //
+  // CONF
+  // dst - X, Immediate
+  // a - 1, Immediate
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200002, 0x00210001, 0x01000401, 0x0E202120 });
+    // 0x4 (2)
+    if (!check(0x4, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}
diff --git a/emulator/tests/modu-instruction.cpp b/emulator/tests/modu-instruction.cpp
new file mode 100644
index 0000000..5a27907
--- /dev/null
+++ b/emulator/tests/modu-instruction.cpp
@@ -0,0 +1,75 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0005
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00200005, 0x0F200220 });
+    if (!check(0x1, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0005
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFFE (-2)
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200005, 0x0021FFFE, 0x0F202120 });
+    if (!check(0x1, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0xFFFE (-2)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0x0005
+  //
+  // DIVI
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x0020FFFE, 0x00210005, 0x0F202120 });
+    if (!check(0xFFFE, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0005 (2.5)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0x0003 (1.5)
+  //
+  // CONF
+  // dst - X, Immediate
+  // a - 1, Immediate
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200005, 0x00210003, 0x01000401, 0x0F202120 });
+
+    if (!check(0x2, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}
diff --git a/emulator/tests/mult-instruction.cpp b/emulator/tests/mult-instruction.cpp
new file mode 100644
index 0000000..4692761
--- /dev/null
+++ b/emulator/tests/mult-instruction.cpp
@@ -0,0 +1,75 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0003
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00200003, 0x0B200220 });
+    if (!check(0x0006, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0007
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFF9 (-7)
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200007, 0x0021FFF9, 0x0B202120 });
+    if (!check(0xFFCF, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0xFFF9 (-7)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFF9 (-7)
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x0020FFF9, 0x0021FFF9, 0x0B202120 });
+    if (!check(0x31, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x0007 (3.5)
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0x0007 (3.5)
+  //
+  // CONF
+  // dst - X, Immediate
+  // a - 1, Immediate
+  //
+  // MULT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00200007, 0x00210007, 0x01000401, 0x0B202120 });
+    // 0x18 (12)
+    if (!check(0x18, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}
diff --git a/emulator/tests/subt-instruction.cpp b/emulator/tests/subt-instruction.cpp
new file mode 100644
index 0000000..5d52f45
--- /dev/null
+++ b/emulator/tests/subt-instruction.cpp
@@ -0,0 +1,36 @@
+#include "test-common.h"
+
+int main(int argc, char** argv)
+{
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x4567
+  //
+  // SUBT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 2, Immediate
+  {
+    foot::Emulator emu = run_instructions({ 0x00204567, 0x0A200220 });
+    if (!check(0x4565, emu.register_at(0))) { return 1; }
+  }
+
+  // CNST
+  // dst - 0, Direct
+  // imm - 0x4567
+  //
+  // CNST
+  // dst - 1, Direct
+  // imm = 0xFFFE (-2)
+  //
+  // SUBT
+  // dst - 0, Direct
+  // a - 0, Direct
+  // b - 1, Direct
+  {
+    foot::Emulator emu = run_instructions({ 0x00204567, 0x0021FFFE, 0x0A202120 });
+    if (!check(0x4569, emu.register_at(0))) { return 1; }
+  }
+
+  return 0;
+}