Address comments.

fpgalib/dac.py

@@ -1203,8 +1203,7 @@ class DAC_Build15(DAC_Build8):
     COUNTER_BYTES = 4
     IDLE_BITS = 15
     JUMP_TABLE_ENTRY_BYTES = 8
-    JUMP_TABLE_COUNT = (JUMP_TABLE_PACKET_LEN - (NUM_COUNTERS * COUNTER_BYTES)
-                        ) / JUMP_TABLE_ENTRY_BYTES
+    JUMP_TABLE_COUNT = 64
     JT_FROM_ADDR_OFFSET = -2
     JT_END_ADDR_OFFSET = JT_FROM_ADDR_OFFSET - 1
     JT_IDLE_OFFSET = -0
@@ -1516,8 +1515,9 @@ def make_jump_table(cls, jt_entries, counters=None, start_address_ns=0):
         :rtype: jump_table.JumpTable
         """
 
-        if len(jt_entries) > cls.JUMP_TABLE_COUNT:
-            raise ValueError("Jump table too long: {} > {}"
+        # -1 hardcoded due to issue #325
+        if len(jt_entries) + 1 > cls.JUMP_TABLE_COUNT:
+            raise ValueError("Jump table too long: {} + starting NOP > {}"
                              .format(len(jt_entries), cls.JUMP_TABLE_COUNT))
 
         # no two opcodes executed within JT_MIN_CLK_CYCLES_BETWEEN_OPCODES
@@ -1547,7 +1547,7 @@ def make_jump_table(cls, jt_entries, counters=None, start_address_ns=0):
             start_addr=cls.convert_to_address(start_address_ns),
             jumps=jt_entries,
             counters=counters,
-            PACKET_LEN=cls.JUMP_TABLE_PACKET_LEN,
+            packet_len=cls.JUMP_TABLE_PACKET_LEN,
         )
 
     @classmethod

fpgalib/jump_table.py

@@ -275,19 +275,19 @@ class JumpTable(object):
     NUM_COUNTERS = 4
 
     def __init__(self, start_addr=None, jumps=None, counters=None,
-                 PACKET_LEN=528):
+                 packet_len=528):
         """
 
         :param start_addr: start address
         :param list[JumpEntry] jumps: the jump table entries
         :param list[int] counters: the counter values
-        :param int PACKET_LEN: Number of packets in a JT write
+        :param int packet_len: Number of byes in jump table write packet
         """
         self._startAddr = 0
         self.counters = self._initialize_counters(counters=counters)
         self.start_addr = start_addr
         self.jumps = jumps
-        self.PACKET_LEN = PACKET_LEN
+        self.packet_len = packet_len
 
     @classmethod
     def _initialize_counters(cls, counters=None):
@@ -323,7 +323,7 @@ def __str__(self):
 
     def toString(self):
         """Serialize jump table to a byte string for the FPGA"""
-        data = np.zeros(self.PACKET_LEN, dtype='<u1')
+        data = np.zeros(self.packet_len, dtype='<u1')
         # Set counter values. Each one is 4 bytes
         for i, c in enumerate(self.counters):
             data[i * 4:(i + 1) * 4] = littleEndian(c, 4)

fpgalib/test/test_dac.py

@@ -100,9 +100,20 @@ def test_nop_nop_min_clk_ok(self):
             ('END', [400])
         ])
 
-    def test_too_many_entry(self):
+    def test_max_entries(self):
         entry_sep = self.dac.JT_MIN_CLK_CYCLES_BETWEEN_OPCODES * 4 * 2
-        from_addr = (entry_sep * np.arange(self.dac.JUMP_TABLE_COUNT + 1) +
+        from_addr = (entry_sep * np.arange(self.dac.JUMP_TABLE_COUNT - 2) +
+                     entry_sep)
+        entries = self.make_entries(
+            [('NOP', [k]) for k in from_addr] +
+            [('END', [from_addr[-1] + entry_sep])]
+        )
+        self.dac.make_jump_table(entries)
+        # we made it this far and we're feeling pretty good about it
+
+    def test_too_many_entries(self):
+        entry_sep = self.dac.JT_MIN_CLK_CYCLES_BETWEEN_OPCODES * 4 * 2
+        from_addr = (entry_sep * np.arange(self.dac.JUMP_TABLE_COUNT - 1) +
                      entry_sep)
         entries = self.make_entries(
             [('NOP', [k]) for k in from_addr] +