From d2ba68881c57d9efb978ba2454f989733b37cb15 Mon Sep 17 00:00:00 2001
From: Andreas Bogk <andreas@oxytocin.(none)>
Date: Sat, 17 Jan 2009 13:14:19 +0100
Subject: A5 implementation in MyHDL.

---
 A5.1/MyHDL/A5.py | 127 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 A5.1/MyHDL/A5.py

diff --git a/A5.1/MyHDL/A5.py b/A5.1/MyHDL/A5.py
new file mode 100644
index 0000000..6530357
--- /dev/null
+++ b/A5.1/MyHDL/A5.py
@@ -0,0 +1,127 @@
+from myhdl import *
+
+def Lfsr(clk, reset, enable, reg, taps):
+    
+    @always(clk.posedge)
+    def shiftRegister():
+        if enable:
+            output = 0
+        
+            for tap in taps:
+                output ^= reg[tap]
+        
+            reg.next = ((reg << 1) + (output & 1)) % reg.max
+
+    return shiftRegister
+
+def printLfsr(clk, reg):
+
+    @always(clk.negedge)
+    def doPrint():
+        print "LFSR value %s" % bin(reg, len(reg))
+
+    return doPrint
+
+def ClkDriver(clk, period=20):
+
+    lowTime = int(period/2)
+    highTime = period - lowTime
+
+    @instance
+    def driveClk():
+        while True:
+            yield delay(lowTime)
+            clk.next = 1
+            yield delay(highTime)
+            clk.next = 0
+
+    return driveClk
+
+def ResetGen(reset, time):
+    @instance
+    def driveReset():
+        reset.next = 0
+        yield delay(time)
+        reset.next = 1
+
+    return driveReset
+
+def Lfsr_tb():
+    clk = Signal(0)
+    reset = Signal(0)
+    oscillator = ClkDriver(clk)
+    reg = Signal(intbv(23)[19:])
+    lfsr = Lfsr(clk, reg, [13, 16, 17, 18], reset)
+    printer = printLfsr(clk, reg)
+    return instances()
+
+def muxReg(clk, reset, reg, R1, R2, R3):
+    return loadReg
+
+def a5(clk, reset, reg):
+
+    R1 = Signal(intbv(0)[19:])
+    R2 = Signal(intbv(0)[22:])
+    R3 = Signal(intbv(0)[23:])
+
+    en1 = Signal(intbv(1)[1:])
+    en2 = Signal(intbv(1)[1:])
+    en3 = Signal(intbv(1)[1:])
+
+    @always(clk.posedge, reset.negedge)
+    def loadReg():
+        if reset == 0:
+            print "Reset"
+            R1.next = reg[64:45]
+            R2.next = reg[45:23]
+            R3.next = reg[23:0]
+        else:
+            reg.next[64:45] = R1
+            reg.next[45:23] = R2
+            reg.next[23:0] = R3
+
+    lfsr1 = Lfsr(clk, reset, en1, R1, [13, 16, 17, 18])
+    lfsr2 = Lfsr(clk, reset, en2, R2, [20, 21])
+    lfsr3 = Lfsr(clk, reset, en3, R3, [7, 20, 21, 22])
+    
+    @always_comb
+    def clock():
+        if R1[8] + R2[10] + R3[10] > 2:
+            en1.next = R1[8]
+            en2.next = R2[10]
+            en3.next = R3[10]
+        else:
+            en1.next = not R1[8]
+            en2.next = not R2[10]
+            en3.next = not R3[10]
+
+
+    return instances()
+
+def a5_tb():
+    clk = Signal(intbv(0)[1:])
+    reset = Signal(intbv(0)[1:])
+    oscillator = ClkDriver(clk)
+    resetgen = ResetGen(reset, 35)
+    reg = Signal(intbv(0xdeadbeefcafebabe)[64:])
+    lfsr = a5(clk, reset, reg)
+    printer = printLfsr(clk, reg)
+    return instances()
+
+
+
+
+
+def sayhello():
+    clk = Signal(0)
+
+    oscillator = ClkDriver(clk)
+
+    hello = Hello(clk)
+
+    return instances()
+
+#inst = a5_tb()
+#sim = Simulation(inst)
+#sim.run()
+a5_inst = toVHDL(a5_tb)
-- 
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