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gateware: fix RAM and ROM issues

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This commit is contained in:
David Lenfesty 2023-03-25 15:21:03 -06:00
parent ac746a8c5a
commit 241cb72553
1 changed files with 15 additions and 1 deletions
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16
gateware/memory.py
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@ -57,6 +57,7 @@ class ROM(Elaboratable, Interface):
class RAM(Elaboratable, Interface):
def __init__(self, *, size_bytes=4096):
addr_width = ceil(log2(size_bytes >> 2))
self.addr_width = addr_width
self.data = Memory(width=32, depth=size_bytes >> 2)
self.r = self.data.read_port()
self.w = self.data.write_port()
@ -81,6 +82,19 @@ class RAM(Elaboratable, Interface):
m.submodules.r = self.r
m.submodules.w = self.w
# TODO not sure if this is the idiomatic way
self.r.en = Const(1)
# Default to not writing data
m.d.sync += self.w.en.eq(0)
# Use read data to populate un-written wishbone data for sub-32-bit reads
for i in range(4):
with m.If(self.sel.bit_select(i, 1)):
m.d.sync += self.w.data.word_select(i, 8).eq(self.dat_w.word_select(i, 8))
with m.Else():
m.d.sync += self.w.data.word_select(i, 8).eq(self.r.data.word_select(i, 8))
# 'ack' signal should rest at 0.
m.d.sync += self.ack.eq(0)
# Simulated reads only take one cycle, but only acknowledge
@ -98,7 +112,7 @@ class RAM(Elaboratable, Interface):
self.r.addr.eq( self.adr ),
self.dat_r.eq( self.r.data ),
self.w.addr.eq(self.adr),
self.w.data.eq(self.dat_w),
#self.w.data.eq(self.dat_w),
]
# End of simulated memory module.