add shadow_fn.py, split out from function unit

diff --git a/src/scoreboard/shadow_fn.py b/src/scoreboard/shadow_fn.py
new file mode 100644 (file)
index 0000000..b29be8c
--- /dev/null
+++ b/src/scoreboard/shadow_fn.py
@@ -0,0 +1,81 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Signal, Cat, Elaboratable
+from nmutil.latch import SRLatch
+from nmigen.lib.coding import Decoder
+
+
+class ShadowFn(Elaboratable):
+    """ implements shadowing 11.5.1, p55, just the individual shadow function
+    """
+    def __init__(self):
+
+        # inputs
+        self.issue_i = Signal(reset_less=True)
+        self.shadow_i  = Signal(reset_less=True)
+        self.s_fail_i  = Signal(reset_less=True)
+        self.s_good_i  = Signal(reset_less=True)
+
+        # outputs
+        self.shadow_o = Signal(reset_less=True)
+        self.recover_o  = Signal(reset_less=True)
+        self.shadow_o  = Signal(reset_less=True)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.sl = sl = SRLatch(sync=False)
+
+        m.d.comb += sl.s.eq(self.shadow_i & self.issue_i)
+        m.d.comb += sl.r.eq(self.s_good_i)
+        m.d.comb += self.recover_o.eq(sl.q & self.s_fail_i)
+        m.d.comb += self.shadow_o.eq(sl.q)
+
+        return m
+
+    def __iter__(self):
+        yield self.issue_i
+        yield self.shadow_i
+        yield self.s_fail_i
+        yield self.s_good_i
+        yield self.shadow_o
+        yield self.recover_o
+        yield self.shadow_o
+
+    def ports(self):
+        return list(self)
+
+
+def shadow_fn_unit_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_shadow_fn_unit():
+    dut = ShadowFn()
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_shadow_fn_unit.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, shadow_fn_unit_sim(dut),
+                   vcd_name='test_shadow_fn_unit.vcd')
+
+if __name__ == '__main__':
+    test_shadow_fn_unit()