From 8e37e1fb36bc8c5e0493ece159aeeb9095bc9c8f Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sat, 8 Jun 2019 07:37:57 +0100
Subject: [PATCH] add fu-mem dependency cell based on fu_dep_cell.py

---
 src/scoreboard/fumem_dep_cell.py | 92 ++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 src/scoreboard/fumem_dep_cell.py

diff --git a/src/scoreboard/fumem_dep_cell.py b/src/scoreboard/fumem_dep_cell.py
new file mode 100644
index 00000000..982b55a3
--- /dev/null
+++ b/src/scoreboard/fumem_dep_cell.py
@@ -0,0 +1,92 @@
+from nmigen.compat.sim import run_simulation
+from nmigen.cli import verilog, rtlil
+from nmigen import Module, Signal, Const, Elaboratable
+from nmutil.latch import SRLatch
+
+
+class FUMemDependenceCell(Elaboratable):
+    """ implements 11.4.7 mitch alsup dependence cell, p27
+    """
+    def __init__(self, dummy, n_fu=1):
+        self.n_fu = n_fu
+        self.dummy = Const(~(1<<dummy), n_fu)
+        # inputs
+        self.st_pend_i = Signal(n_fu, reset_less=True) # read pend in (left)
+        self.ld_pend_i = Signal(n_fu, reset_less=True) # write pend in (left)
+        self.issue_i = Signal(n_fu, reset_less=True)    # Issue in (top)
+
+        self.go_ld_i = Signal(n_fu, reset_less=True) # Go Write in (left)
+        self.go_st_i = Signal(n_fu, reset_less=True)  # Go Read in (left)
+        self.go_die_i = Signal(n_fu, reset_less=True) # Go Die in (left)
+
+        # outputs (latched rd/wr wait)
+        self.st_wait_o = Signal(n_fu, reset_less=True) # read wait out (right)
+        self.ld_wait_o = Signal(n_fu, reset_less=True) # write wait out (right)
+
+    def elaborate(self, platform):
+        m = Module()
+        m.submodules.st_c = st_c = SRLatch(sync=False, llen=self.n_fu)
+        m.submodules.ld_c = ld_c = SRLatch(sync=False, llen=self.n_fu)
+
+        # reset on go HI, set on dest and issue
+        m.d.comb += st_c.s.eq(self.issue_i & self.st_pend_i)
+        m.d.comb += ld_c.s.eq(self.issue_i & self.ld_pend_i)
+
+        # connect go_rd / go_wr 
+        m.d.comb += ld_c.r.eq(self.go_ld_i | self.go_die_i)
+        m.d.comb += st_c.r.eq(self.go_st_i | self.go_die_i)
+
+        # connect pend_i
+        m.d.comb += st_c.s.eq(self.issue_i & self.st_pend_i & self.dummy)
+        m.d.comb += ld_c.s.eq(self.issue_i & self.ld_pend_i & self.dummy)
+
+        # connect output
+        m.d.comb += self.st_wait_o.eq(st_c.qlq & ~self.issue_i)
+        m.d.comb += self.ld_wait_o.eq(ld_c.qlq & ~self.issue_i)
+
+        return m
+
+    def __iter__(self):
+        yield self.st_pend_i
+        yield self.ld_pend_i
+        yield self.issue_i
+        yield self.go_ld_i
+        yield self.go_st_i
+        yield self.go_die_i
+        yield self.st_wait_o
+        yield self.ld_wait_o
+                
+    def ports(self):
+        return list(self)
+
+
+def dcell_sim(dut):
+    yield dut.ld_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.st_i.eq(1)
+    yield dut.issue_i.eq(1)
+    yield
+    yield dut.issue_i.eq(0)
+    yield
+    yield dut.go_st_i.eq(1)
+    yield
+    yield dut.go_st_i.eq(0)
+    yield
+    yield dut.go_ld_i.eq(1)
+    yield
+    yield dut.go_ld_i.eq(0)
+    yield
+
+def test_dcell():
+    dut = FUMemDependenceCell(dummy=0, n_fu=4)
+    vl = rtlil.convert(dut, ports=dut.ports())
+    with open("test_fumem_dcell.il", "w") as f:
+        f.write(vl)
+
+    run_simulation(dut, dcell_sim(dut), vcd_name='test_fumem_dcell.vcd')
+
+if __name__ == '__main__':
+    test_dcell()
-- 
2.30.2