basic shift register working

3 files changed, 180 insertions, 0 deletions

diff --git a/hdl/testing/shift_reg.py b/hdl/testing/shift_reg.py
new file mode 100644
index 0000000..b7c2290
--- /dev/null
+++ b/hdl/testing/shift_reg.py
@@ -0,0 +1,100 @@
+import sys
+from amaranth import *
+from amaranth.back import verilog, cxxrtl
+from amaranth.cli import main
+from amaranth.sim import Simulator, Settle, Delay
+
+BASENAME = "shift_reg"
+
+class ShiftReg(Elaboratable):
+    def __init__(self, width):
+        self.load_val = Signal(width, reset=0, reset_less=True)
+        self.load = Signal()
+        self.reg = Signal(width)
+        self.en = Signal()
+        self.right_left = Signal()
+
+        self.ports = [self.load_val, self.en, self.right_left, self.reg]
+
+    def elaborate(self, platform):
+        m = Module()
+
+        with m.If(self.load):
+            m.d.sync += self.reg.eq(self.load_val)
+        with m.Else():
+            with m.If(self.en):
+                with m.If(self.right_left):
+                    m.d.sync += self.reg.eq(self.reg << 1)
+                with m.Else():
+                    m.d.sync += self.reg.eq(self.reg >> 1)
+
+        return m
+
+
+def step():
+    yield
+    yield Settle()
+
+def test_shift_reg():
+    dut = ShiftReg(8)
+
+    def proc1():
+        val = 0xAB
+
+        yield dut.load_val.eq(val)
+        yield dut.en.eq(0)
+        yield dut.load.eq(1)
+        yield
+        yield Settle()
+        yield dut.load.eq(0)
+        yield dut.en.eq(1)   
+
+        for _ in range(9):
+            reg_val = yield dut.reg
+            assert reg_val == val, f"Incorrect shift ---EXPECTED: {hex(val)}   ---GOT: {hex(reg_val)}"
+            val = val >> 1
+            yield
+            yield Settle()
+
+        val = 0xBD
+        yield dut.load_val.eq(val)
+        yield dut.load.eq(1)
+        yield dut.right_left.eq(1)
+        yield
+        yield Settle()
+        yield dut.load.eq(0)
+
+        for _ in range(9):
+            reg_val = yield dut.reg
+            assert reg_val == val, f"Incorrect shift ---EXPECTED: {hex(val)}   ---GOT: {hex(reg_val)}"
+            val = (val << 1) & 0xff
+            yield
+            yield Settle()
+
+
+
+    sim = Simulator(dut)
+    sim.add_clock(1e-6)
+    sim.add_sync_process(proc1)
+    
+    with sim.write_vcd(BASENAME + '.vcd'):
+        sim.run()
+
+
+if __name__ == '__main__':
+
+    if sys.argv[1] == "sim":
+        test_shift_reg()
+        exit()
+
+    m = ShiftReg(8)
+
+    if sys.argv[1] == "v":
+        out = verilog.convert(m, ports=m.ports)
+        with open(BASENAME + '.v','w') as f:
+            f.write(out)
+    
+    elif sys.argv[1] == "cc":
+        out = cxxrtl.convert(m, ports=m.ports)
+        with open(BASENAME + '.cc','w') as f:
+            f.write(out)
diff --git a/hdl/testing/up_counter.py b/hdl/testing/up_counter.py
new file mode 100644
index 0000000..050a6b0
--- /dev/null
+++ b/hdl/testing/up_counter.py
@@ -0,0 +1,50 @@
+from amaranth import *
+from amaranth.back import verilog
+
+
+class UpCounter(Elaboratable):
+    """
+    A 16-bit up counter with a fixed limit.
+
+    Parameters
+    ----------
+    limit : int
+        The value at which the counter overflows.
+
+    Attributes
+    ----------
+    en : Signal, in
+        The counter is incremented if ``en`` is asserted, and retains
+        its value otherwise.
+    ovf : Signal, out
+        ``ovf`` is asserted when the counter reaches its limit.
+    """
+    
+    def __init__(self, limit):
+        self.limit = limit
+
+        # Ports
+        self.en  = Signal()
+        self.ovf = Signal()
+
+        # State
+        self.count = Signal(16)
+
+    def elaborate(self, platform):
+        m = Module()
+
+        m.d.comb += self.ovf.eq(self.count == self.limit)
+
+        with m.If(self.en):
+            with m.If(self.ovf):
+                m.d.sync += self.count.eq(0)
+            with m.Else():
+                m.d.sync += self.count.eq(self.count + 1)
+
+        return m
+
+    def to_v(self):
+        return verilog.convert(self, ports=[self.en, self.ovf])
+
+top = UpCounter(25)
+print(top.to_v())
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diff --git a/hdl/testing/up_counter_tb.py b/hdl/testing/up_counter_tb.py
new file mode 100644
index 0000000..7c2e8d2
--- /dev/null
+++ b/hdl/testing/up_counter_tb.py
@@ -0,0 +1,30 @@
+from amaranth.sim import Simulator
+from up_counter import UpCounter
+
+dut = UpCounter(25)
+
+
+def bench():
+    # Disabled counter should not overflow.
+    yield dut.en.eq(0)
+    for _ in range(30):
+        yield
+        assert not (yield dut.ovf)
+
+    # Once enabled, the counter should overflow in 25 cycles.
+    yield dut.en.eq(1)
+    for _ in range(25):
+        yield
+        assert not (yield dut.ovf)
+    yield
+    assert (yield dut.ovf)
+
+    # The overflow should clear in one cycle.
+    yield
+    assert not (yield dut.ovf)
+
+sim = Simulator(dut)
+sim.add_clock(1e-6) # 1 MHz
+sim.add_sync_process(bench)
+with sim.write_vcd("up_counter.vcd"):
+    sim.run()
\ No newline at end of file