From d30f87d788f953fdac4db971da41d3d09cfc6807 Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sat, 23 Feb 2019 11:30:44 +0000
Subject: [PATCH] add a dual-chained add experiment

---
 src/add/dual_add_experiment.py | 83 ++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 src/add/dual_add_experiment.py

diff --git a/src/add/dual_add_experiment.py b/src/add/dual_add_experiment.py
new file mode 100644
index 00000000..136294d3
--- /dev/null
+++ b/src/add/dual_add_experiment.py
@@ -0,0 +1,83 @@
+from nmigen import *
+from nmigen.cli import main
+
+from nmigen_add_experiment import FPADD
+from fpbase import FPOp
+
+
+class Adder:
+    def __init__(self, width):
+        self.a   = Signal(width)
+        self.b   = Signal(width)
+        self.o   = Signal(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.d.comb += self.o.eq(self.a + self.b)
+        return m
+
+
+class Subtractor:
+    def __init__(self, width):
+        self.a   = Signal(width)
+        self.b   = Signal(width)
+        self.o   = Signal(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.d.comb += self.o.eq(self.a - self.b)
+        return m
+
+
+class ALU:
+    def __init__(self, width):
+        #self.op  = Signal()
+        self.a   = FPOp(width)
+        self.b   = FPOp(width)
+        self.c   = FPOp(width)
+        self.z   = FPOp(width)
+
+        self.add1 = FPADD(width)
+        self.add2 = FPADD(width)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.add1 = self.add1
+        m.submodules.add2 = self.add2
+        m.d.comb += [
+            # join add1 a to a
+            self.add1.in_a.v.eq(self.a.v),
+            self.add1.in_a.stb.eq(self.a.stb),
+            # join add1 b to b
+            self.add1.in_b.v.eq(self.b.v),
+            self.add1.in_b.stb.eq(self.b.stb),
+            # join add2 a to c
+            self.add2.in_a.v.eq(self.c.v),
+            self.add2.in_a.stb.eq(self.c.stb),
+            # join add2 b to add1 z
+            self.add2.in_b.v.eq(self.add1.out_z.v),
+            self.add2.in_b.stb.eq(self.add1.out_z.stb),
+        ]
+        m.d.sync += [
+            # join add1 a to a
+            self.add1.in_a.ack.eq(self.a.ack),
+            # join add1 b to b
+            self.add1.in_b.ack.eq(self.b.ack),
+            # join add2 a to c
+            self.add2.in_a.ack.eq(self.c.ack),
+            # join add2 b to add1 z
+            self.add2.in_b.ack.eq(self.add1.out_z.ack),
+        ]
+        #with m.If(self.op):
+        #    m.d.comb += self.o.eq(self.sub.o)
+        #with m.Else():
+        #    m.d.comb += self.o.eq(self.add.o)
+        return m
+
+
+if __name__ == "__main__":
+    alu = ALU(width=16)
+    main(alu, ports=alu.a.ports() + \
+                     alu.b.ports() + \
+                     alu.c.ports() + \
+                     alu.z.ports())
-- 
2.30.2