litex/misoc/cores/spi_flash.py

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from migen import *
from migen.genlib.misc import timeline
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from misoc.interconnect import wishbone
from misoc.interconnect.csr import AutoCSR, CSRStorage, CSRStatus
_FAST_READ = 0x0b
_DIOFR = 0xbb
_QIOFR = 0xeb
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def _format_cmd(cmd, spi_width):
"""
`cmd` is the read instruction. Since everything is transmitted on all
dq lines (cmd, adr and data), extend/interleave cmd to full pads.dq
width even if dq1-dq3 are don't care during the command phase:
For example, for N25Q128, 0xeb is the quad i/o fast read, and
extended to 4 bits (dq1,dq2,dq3 high) is: 0xfffefeff
"""
c = 2**(8*spi_width)-1
for b in range(8):
if not (cmd>>b)%2:
c &= ~(1<<(b*spi_width))
return c
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class SpiFlash(Module, AutoCSR):
def __init__(self, pads, dummy=15, div=2, with_bitbang=True):
"""
Simple SPI flash, e.g. N25Q128 on the LX9 Microboard.
Supports multi-bit pseudo-parallel reads (aka Dual or Quad I/O Fast
Read). Only supports mode0 (cpol=0, cpha=0).
Optionally supports software bitbanging (for write, erase, or other commands).
"""
self.bus = bus = wishbone.Interface()
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spi_width = len(pads.dq)
if with_bitbang:
self.bitbang = CSRStorage(4)
self.miso = CSRStatus()
self.bitbang_en = CSRStorage()
###
cs_n = Signal(reset=1)
clk = Signal()
dq_oe = Signal()
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wbone_width = len(bus.dat_r)
read_cmd_params = {
4: (_format_cmd(_QIOFR, 4), 4*8),
2: (_format_cmd(_DIOFR, 2), 2*8),
1: (_format_cmd(_FAST_READ, 1), 1*8)
}
read_cmd, cmd_width = read_cmd_params[spi_width]
addr_width = 24
pads.cs_n.reset = 1
dq = TSTriple(spi_width)
self.specials.dq = dq.get_tristate(pads.dq)
sr = Signal(max(cmd_width, addr_width, wbone_width))
dqs = Replicate(1, spi_width-1)
self.comb += bus.dat_r.eq(sr)
hw_read_logic = [
pads.clk.eq(clk),
pads.cs_n.eq(cs_n),
dq.o.eq(sr[-spi_width:]),
dq.oe.eq(dq_oe)
]
if with_bitbang:
bitbang_logic = [
pads.clk.eq(self.bitbang.storage[1]),
pads.cs_n.eq(self.bitbang.storage[2]),
dq.o.eq(Cat(self.bitbang.storage[0], dqs)),
If(self.bitbang.storage[3],
dq.oe.eq(0)
).Else(
dq.oe.eq(1)
),
If(self.bitbang.storage[1],
self.miso.status.eq(dq.i[1])
)
]
self.comb += \
If(self.bitbang_en.storage,
bitbang_logic
).Else(
hw_read_logic
)
else:
self.comb += hw_read_logic
if div < 2:
raise ValueError("Unsupported value \'{}\' for div parameter for SpiFlash core".format(div))
else:
i = Signal(max=div)
dqi = Signal(spi_width)
self.sync += [
If(i == div//2 - 1,
clk.eq(1),
dqi.eq(dq.i),
),
If(i == div - 1,
i.eq(0),
clk.eq(0),
sr.eq(Cat(dqi, sr[:-spi_width]))
).Else(
i.eq(i + 1),
),
]
# spi is byte-addressed, prefix by zeros
z = Replicate(0, log2_int(wbone_width//8))
seq = [
(cmd_width//spi_width*div,
[dq_oe.eq(1), cs_n.eq(0), sr[-cmd_width:].eq(read_cmd)]),
(addr_width//spi_width*div,
[sr[-addr_width:].eq(Cat(z, bus.adr))]),
((dummy + wbone_width//spi_width)*div,
[dq_oe.eq(0)]),
(1,
[bus.ack.eq(1), cs_n.eq(1)]),
(div, # tSHSL!
[bus.ack.eq(0)]),
(0,
[]),
]
# accumulate timeline deltas
t, tseq = 0, []
for dt, a in seq:
tseq.append((t, a))
t += dt
self.sync += timeline(bus.cyc & bus.stb & (i == div - 1), tseq)