soc/cores: add initial NX-LRAM support.

litex/soc/cores/nxlram.py

@@ -0,0 +1,67 @@
+#
+# This file is part of LiteX.
+#
+# Copyright (c) 2020 Piense <piense@gmail.com>
+# Copyright (c) 2019 William D. Jones <thor0505@comcast.net>
+# Copyright (c) 2019 Tim 'mithro' Ansell <me@mith.ro>
+# Copyright (c) 2019 Florent Kermarrec <florent@enjoy-digital.fr>
+# SPDX-License-Identifier: BSD-2-Clause
+
+from migen import *
+from litex.soc.interconnect import wishbone
+
+kB = 1024
+
+"""
+NX family-specific Wishbone interface to the LRAM primitive.
+
+Each LRAM is 64kBytes arranged in 32 bit wide words.
+
+Note that this memory is dual port, but we only use a single port in this
+instantiation.
+"""
+
+class NXLRAM(Module):
+    def __init__(self, width=32, size=128*kB):
+        self.bus = wishbone.Interface(width)
+        assert width in [32, 64]
+
+        # TODO: allow larger sizes to support Crosslink/NX-17 & Certus
+        if width == 32:
+            assert size in [64*kB, 128*kB]
+            depth_cascading = size//(64*kB)
+            width_cascading = 1
+        if width == 64:
+            assert size in [128*kB]
+            depth_cascading = size//(128*kB)
+            width_cascading = 2
+
+        for d in range(depth_cascading):
+            for w in range(width_cascading):
+                datain = Signal(32)
+                dataout = Signal(32)
+                cs = Signal()
+                wren = Signal()
+                self.comb += [
+                    cs.eq(self.bus.adr[14:14+log2_int(depth_cascading)+1] == d),
+                    wren.eq(self.bus.we & self.bus.stb & self.bus.cyc),
+                    datain.eq(self.bus.dat_w[32*w:32*(w+1)]),
+                    If(cs,
+                        self.bus.dat_r[32*w:32*(w+1)].eq(dataout)
+                    ),
+                ]
+                self.specials += Instance("SP512K",
+                    p_ECC_BYTE_SEL = "BYTE_EN",
+                    i_DI       = datain,
+                    i_AD       = self.bus.adr[:14],
+                    i_CLK      = ClockSignal(),
+                    i_CE       = 0b1,
+                    i_WE       = wren,
+                    i_CS       = cs,
+                    i_RSTOUT   = 0b0,
+                    i_CEOUT    = 0b0,
+                    i_BYTEEN_N = ~self.bus.sel[4*w:4*(w+1)],
+                    o_DO       = dataout
+                )
+
+        self.sync += self.bus.ack.eq(self.bus.stb & self.bus.cyc & ~self.bus.ack)