add computational unit

diff --git a/src/experiment/compalu.py b/src/experiment/compalu.py
new file mode 100644 (file)
index 0000000..dd72ecd
--- /dev/null
+++ b/src/experiment/compalu.py
@@ -0,0 +1,95 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Signal, Elaboratable
+
+from nmutil.latch import SRLatch
+
+
+class ComputationUnitNoDelay(Elaboratable):
+    def __init__(self, rwid, opwid, alu):
+        self.rwid = rwid
+        self.alu = alu
+
+        self.go_rd_i = Signal(reset_less=True) # go read in
+        self.go_wr_i = Signal(reset_less=True) # go write in
+        self.issue_i = Signal(reset_less=True) # fn issue in
+
+        self.oper_i = Signal(opwid, reset_less=True) # opcode in
+        self.src1_i = Signal(rwid, reset_less=True) # oper1 in
+        self.src2_i = Signal(rwid, reset_less=True) # oper2 in
+
+        self.busy_o = Signal(reset_less=True) # fn busy out
+        self.data_o = Signal(rwid, reset_less=True) # Dest out
+        self.req_rel_o = Signal(reset_less=True) # release request out (valid_o)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.alu = self.alu
+        m.submodules.src_l = src_l = SRLatch(sync=False)
+        m.submodules.opc_l = opc_l = SRLatch(sync=False)
+        m.submodules.req_l = req_l = SRLatch(sync=False)
+
+        # This is fascinating and very important to observe that this
+        # is in effect a "3-way revolving door".  At no time may all 3
+        # latches be set at the same time.
+
+        # opcode latch (not using go_rd_i)
+        m.d.comb += opc_l.s.eq(self.go_wr_i)
+        m.d.comb += opc_l.r.eq(self.issue_i)
+
+        # src operand latch (not using go_wr_i)
+        m.d.comb += src_l.s.eq(self.issue_i)
+        m.d.comb += src_l.r.eq(self.go_rd_i)
+
+        # dest operand latch (not using issue_i)
+        m.d.comb += req_l.s.eq(self.go_rd_i)
+        m.d.comb += req_l.r.eq(self.go_wr_i)
+
+        # outputs
+        m.d.comb += self.busy_o.eq(opc_l.qn) # busy out
+        m.d.comb += self.req_rel_o.eq(req_l.qn & opc_l.q) # request release out
+
+        with m.If(src_l.q):
+            m.d.comb += self.alu.a.eq(self.src1_i)
+            m.d.comb += self.alu.b.eq(self.src2_i)
+
+        with m.If(opc_l.q):
+            m.d.comb += self.alu.op.eq(self.oper_i)
+
+        with m.If(req_l.qn):
+            m.d.comb += self.data_o.eq(self.alu.o)
+
+        return m
+
+def scoreboard_sim(dut):
+    yield dut.dest_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.src1_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.go_read_i.eq(1)
+    yield
+    yield dut.go_read_i.eq(0)
+    yield
+    yield dut.go_write_i.eq(1)
+    yield
+    yield dut.go_write_i.eq(0)
+    yield
+
+def test_scoreboard():
+    dut = Scoreboard(32, 8)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_scoreboard.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, scoreboard_sim(dut), vcd_name='test_scoreboard.vcd')
+
+if __name__ == '__main__':
+    test_scoreboard()