test/test_prbs: add PRBSGenerator/Checker tests

test/test_prbs.py

+import unittest
+
+from migen import *
+
+from litex.soc.cores.prbs import *
+
+
+class PRBSModel:
+    def __init__(self, n_state=23, taps=[17, 22]):
+        self.n_state = n_state
+        self.taps = taps
+        self.state = 1
+
+    def getbit(self):
+        feedback = 0
+        for tap in self.taps:
+            feedback = feedback ^ (self.state >> tap) & 0x1
+        self.state = (self.state << 1) & (2**self.n_state-1) | feedback
+        return feedback
+
+    def getbits(self, n):
+        v = 0
+        for i in range(n):
+            v <<= 1
+            v |= self.getbit()
+        return v
+
+
+class PRBS7Model(PRBSModel):
+    def __init__(self):
+        PRBSModel.__init__(self, n_state=7,  taps=[5, 6])
+
+
+class PRBS15Model(PRBSModel):
+    def __init__(self):
+        PRBSModel.__init__(self, n_state=15,  taps=[13, 14])
+
+
+class PRBS31Model(PRBSModel):
+    def __init__(self):
+        PRBSModel.__init__(self, n_state=31,  taps=[27, 30])
+
+
+class TestPRBS(unittest.TestCase):
+    def test_prbs_generator(self):
+        duts = {
+            "prbs7":  PRBS7Generator(8),
+            "prbs15": PRBS15Generator(16),
+            "prbs31": PRBS31Generator(32),
+        }
+        models = {
+            "prbs7":  PRBS7Model(),
+            "prbs15": PRBS15Model(),
+            "prbs31": PRBS31Model(),
+        }
+        errors = 0
+        for test in ["prbs7", "prbs15", "prbs31"]:
+            dut = duts[test]
+            dut._errors = 0
+            model = models[test]
+            def checker(dut, cycles):
+                yield
+                # Let the generator run and check values against model.
+                for i in range(cycles):
+                    if (yield dut.o) != model.getbits(len(dut.o)):
+                        dut._errors += 1
+                    yield
+            run_simulation(dut, checker(dut, 1024))
+            self.assertEqual(dut._errors, 0)
+
+    def test_prbs_checker(self):
+        duts = {
+            "prbs7":  PRBS7Checker(8),
+            "prbs15": PRBS15Checker(16),
+            "prbs31": PRBS31Checker(32),
+        }
+        models = {
+            "prbs7":  PRBS7Model(),
+            "prbs15": PRBS15Model(),
+            "prbs31": PRBS31Model(),
+        }
+        errors = 0
+        for test in ["prbs7", "prbs15", "prbs31"]:
+            dut = duts[test]
+            dut._errors = 0
+            model = models[test]
+            @passive
+            def generator(dut):
+                # Inject PRBS values from model.
+                while True:
+                    yield dut.i.eq(model.getbits(len(dut.i)))
+                    yield
+            def checker(dut, cycles):
+                # Wait PRBS synchronization.
+                for i in range(8):
+                    yield
+                # Check that no errors are reported.
+                for i in range(cycles):
+                    if (yield dut.errors) != 0:
+                        dut._errors += 1
+                    yield
+            run_simulation(dut, [generator(dut), checker(dut, 1024)])
+            self.assertEqual(dut._errors, 0)