+class DualPortRegfile(Elaboratable):
+ """
+ Builds, from a pair of phased 1W/1R blocks, a true 1W/1R RAM, where both
+ read and write ports work every cycle.
+ It employs a Last Value Table, that tracks to which memory each address was
+ last written.
+
+ :param addr_width: width of the address bus
+ :param data_width: width of the data bus
+ :param we_width: number of write enable lines
+ """
+
+ def __init__(self, addr_width, data_width, we_width):
+ self.addr_width = addr_width
+ self.data_width = data_width
+ self.we_width = we_width
+ self.wr_addr_i = Signal(addr_width); """write port address"""
+ self.wr_data_i = Signal(data_width); """write port data"""
+ self.wr_we_i = Signal(we_width); """write port enable"""
+ self.rd_addr_i = Signal(addr_width); """read port address"""
+ self.rd_data_o = Signal(data_width); """read port data"""
+
+ def elaborate(self, _):
+ m = Module()
+ # depth and granularity
+ depth = 1 << self.addr_width
+ gran = self.data_width // self.we_width
+ # instantiate the two phased 1R/1W memory blocks
+ mem0 = PhasedDualPortRegfile(
+ self.addr_width, self.data_width, self.we_width, 0, False)
+ mem1 = PhasedDualPortRegfile(
+ self.addr_width, self.data_width, self.we_width, 1, False)
+ m.submodules.mem0 = mem0
+ m.submodules.mem1 = mem1
+ # instantiate the backing memory (FFRAM or LUTRAM)
+ # for the Last Value Table
+ # it should have the same number and port types of the desired
+ # memory, but just one bit per write lane
+ lvt_mem = Memory(width=self.we_width, depth=depth)
+ lvt_wr = lvt_mem.write_port(granularity=1)
+ lvt_rd = lvt_mem.read_port(transparent=False)
+ m.submodules.lvt_wr = lvt_wr
+ m.submodules.lvt_rd = lvt_rd
+ # generate and wire the phases for the phased memories
+ phase = Signal()
+ m.d.sync += phase.eq(~phase)
+ m.d.comb += [
+ mem0.phase.eq(phase),
+ mem1.phase.eq(phase),
+ ]
+ m.d.comb += [
+ # wire the write ports, directly
+ mem0.wr_addr_i.eq(self.wr_addr_i),
+ mem1.wr_addr_i.eq(self.wr_addr_i),
+ mem0.wr_we_i.eq(self.wr_we_i),
+ mem1.wr_we_i.eq(self.wr_we_i),
+ mem0.wr_data_i.eq(self.wr_data_i),
+ mem1.wr_data_i.eq(self.wr_data_i),
+ # also wire the read addresses
+ mem0.rd_addr_i.eq(self.rd_addr_i),
+ mem1.rd_addr_i.eq(self.rd_addr_i),
+ # wire read and write ports to the LVT
+ lvt_wr.addr.eq(self.wr_addr_i),
+ lvt_wr.en.eq(self.wr_we_i),
+ lvt_rd.addr.eq(self.rd_addr_i),
+ # the data for the LVT is the phase on which the value was
+ # written
+ lvt_wr.data.eq(Repl(phase, self.we_width)),
+ ]
+ for i in range(self.we_width):
+ # select the right memory to assign to the output read port,
+ # in this byte lane, according to the LVT contents
+ m.d.comb += self.rd_data_o.word_select(i, gran).eq(
+ Mux(
+ lvt_rd.data[i],
+ mem1.rd_data_o.word_select(i, gran),
+ mem0.rd_data_o.word_select(i, gran)))
+ return m
+
+
+class DualPortRegfileTestCase(FHDLTestCase):
+
+ def test_dual_port_regfile(self):
+ """
+ Simulate some read/write/modify operations on the dual port register
+ file
+ """
+ dut = DualPortRegfile(7, 32, 4)
+ sim = Simulator(dut)
+ sim.add_clock(1e-6)
+
+ expected = None
+ last_expected = None
+
+ # compare read data with previously written data
+ # and start a new read
+ def read(rd_addr_i, next_expected=None):
+ nonlocal expected, last_expected
+ if expected is not None:
+ self.assertEqual((yield dut.rd_data_o), expected)
+ yield dut.rd_addr_i.eq(rd_addr_i)
+ # account for the read latency
+ expected = last_expected
+ last_expected = next_expected
+
+ # start a write
+ def write(wr_addr_i, wr_we_i, wr_data_i):
+ yield dut.wr_addr_i.eq(wr_addr_i)
+ yield dut.wr_we_i.eq(wr_we_i)
+ yield dut.wr_data_i.eq(wr_data_i)
+
+ def process():
+ # write a pair of values, one for each memory
+ yield from read(0)
+ yield from write(0x42, 0b1111, 0x87654321)
+ yield
+ yield from read(0x42, 0x87654321)
+ yield from write(0x43, 0b1111, 0x0FEDCBA9)
+ yield
+ # skip a beat
+ yield from read(0x43, 0x0FEDCBA9)
+ yield from write(0, 0, 0)
+ yield
+ # write again, but now they switch memories
+ yield from read(0)
+ yield from write(0x42, 0b1111, 0x12345678)
+ yield
+ yield from read(0x42, 0x12345678)
+ yield from write(0x43, 0b1111, 0x9ABCDEF0)
+ yield
+ yield from read(0x43, 0x9ABCDEF0)
+ yield from write(0, 0, 0)
+ yield
+ # test partial writes
+ yield from read(0)
+ yield from write(0x42, 0b1001, 0x78FFFF12)
+ yield
+ yield from read(0)
+ yield from write(0x43, 0b0110, 0xFFDEABFF)
+ yield
+ yield from read(0x42, 0x78345612)
+ yield from write(0, 0, 0)
+ yield
+ yield from read(0x43, 0x9ADEABF0)
+ yield from write(0, 0, 0)
+ yield
+ yield from read(0)
+ yield from write(0, 0, 0)
+ yield
+ # test non-transparent reads
+ yield from read(0x42, 0x78345612)
+ yield from write(0x42, 0b1111, 0x55AA9966)
+ yield
+ yield from read(0x42, 0x55AA9966)
+ yield from write(0, 0, 0)
+ yield
+ yield from read(0)
+ yield from write(0, 0, 0)
+ yield
+ yield from read(0)
+ yield from write(0, 0, 0)
+
+ sim.add_sync_process(process)
+ debug_file = 'test_dual_port_regfile'
+ traces = ['clk', 'phase',
+ {'comment': 'write port'},
+ 'wr_addr_i[6:0]', 'wr_we_i[3:0]', 'wr_data_i[31:0]',
+ {'comment': 'read port'},
+ 'rd_addr_i[6:0]', 'rd_data_o[31:0]',
+ {'comment': 'LVT write port'},
+ 'phase', 'lvt_mem_w_addr[6:0]', 'lvt_mem_w_en[3:0]',
+ 'lvt_mem_w_data[3:0]',
+ {'comment': 'LVT read port'},
+ 'lvt_mem_r_addr[6:0]', 'lvt_mem_r_data[3:0]',
+ {'comment': 'backing memory'},
+ 'mem0.rd_data_o[31:0]',
+ 'mem1.rd_data_o[31:0]',
+ ]
+ write_gtkw(debug_file + '.gtkw',
+ debug_file + '.vcd',
+ traces, module='top', zoom=-22)
+ sim_writer = sim.write_vcd(debug_file + '.vcd')
+ with sim_writer:
+ sim.run()
+
+
projects / soc.git / commitdiff