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artiq/soc/artiqlib/ad9858.py

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from migen.fhdl.std import *
from migen.genlib.fsm import *
from migen.bus import wishbone
from migen.bus.transactions import *
from migen.sim.generic import run_simulation
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class AD9858(Module):
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"""Wishbone interface to the AD9858 DDS chip.
Addresses 0-63 map the AD9858 registers.
Data is zero-padded.
Write to address 64 to pulse the FUD signal.
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Address 65 is a GPIO register that controls the sel, p and reset signals.
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sel is mapped to the lower bits, followed by p and reset.
Write timing:
Address is set one cycle before assertion of we_n.
we_n is asserted for one cycle, at the same time as valid data is driven.
Read timing:
Address is set one cycle before assertion of rd_n.
rd_n is asserted for 3 cycles.
Data is sampled 2 cycles into the assertion of rd_n.
Design:
All IO pads are registered.
LVDS driver/receiver propagation delays are 3.6+4.5 ns max
LVDS state transition delays are 20, 15 ns max
Schmitt trigger delays are 6.4ns max
Round-trip addr A setup (> RX, RD, D to Z), RD prop, D valid (< D
valid), D prop is ~15 + 10 + 20 + 10 = 55ns
"""
def __init__(self, pads, drive_fud=False, bus=None):
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if bus is None:
bus = wishbone.Interface()
self.bus = bus
# # #
dts = TSTriple(8)
self.specials += dts.get_tristate(pads.d)
dr = Signal(8)
rx = Signal()
self.sync += [
pads.a.eq(bus.adr),
dts.o.eq(bus.dat_w),
dr.eq(dts.i),
dts.oe.eq(~rx)
]
gpio = Signal(flen(pads.sel) + flen(pads.p) + 1)
gpio_load = Signal()
self.sync += If(gpio_load, gpio.eq(bus.dat_w))
self.comb += [
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Cat(pads.sel, pads.p).eq(gpio),
pads.rst_n.eq(~gpio[-1]),
]
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bus_r_gpio = Signal()
self.comb += If(bus_r_gpio,
bus.dat_r.eq(gpio)
).Else(
bus.dat_r.eq(dr)
)
if drive_fud:
fud = Signal()
self.sync += pads.fud_n.eq(~fud)
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pads.wr_n.reset = 1
pads.rd_n.reset = 1
wr = Signal()
rd = Signal()
self.sync += pads.wr_n.eq(~wr), pads.rd_n.eq(~rd)
fsm = FSM("IDLE")
self.submodules += fsm
fsm.act("IDLE",
If(bus.cyc & bus.stb,
If(bus.adr[6],
If(bus.adr[0],
NextState("GPIO")
).Else(
NextState("FUD") if drive_fud else None
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)
).Else(
If(bus.we,
NextState("WRITE")
).Else(
NextState("READ")
)
)
)
)
fsm.act("WRITE",
# 3ns A setup to WR active
wr.eq(1),
NextState("WRITE0")
)
fsm.act("WRITE0",
# 3.5ns D setup to WR inactive
# 0ns D and A hold to WR inactive
bus.ack.eq(1),
NextState("IDLE")
)
fsm.act("READ",
# 15ns D valid to A setup
# 15ns D valid to RD active
rx.eq(1),
rd.eq(1),
NextState("READ0")
)
fsm.act("READ0",
rx.eq(1),
rd.eq(1),
NextState("READ1")
)
fsm.act("READ1",
rx.eq(1),
rd.eq(1),
NextState("READ2")
)
fsm.act("READ2",
rx.eq(1),
rd.eq(1),
NextState("READ3")
)
fsm.act("READ3",
rx.eq(1),
rd.eq(1),
NextState("READ4")
)
fsm.act("READ4",
rx.eq(1),
NextState("READ5")
)
fsm.act("READ5",
# 5ns D three-state to RD inactive
# 10ns A hold to RD inactive
rx.eq(1),
bus.ack.eq(1),
NextState("IDLE")
)
if drive_fud:
fsm.act("FUD",
# 4ns FUD setup to SYNCLK
# 0ns FUD hold to SYNCLK
fud.eq(1),
bus.ack.eq(1),
NextState("IDLE")
)
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fsm.act("GPIO",
bus.ack.eq(1),
bus_r_gpio.eq(1),
If(bus.we, gpio_load.eq(1)),
NextState("IDLE")
)
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def _test_gen():
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# Test external bus writes
yield TWrite(4, 2)
yield TWrite(5, 3)
yield
# Test external bus reads
yield TRead(14)
yield TRead(15)
yield
# Test FUD
yield TWrite(64, 0)
yield
# Test GPIO
yield TWrite(65, 0xff)
yield
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class _TestPads:
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def __init__(self):
self.a = Signal(6)
self.d = Signal(8)
self.sel = Signal(5)
self.p = Signal(2)
self.fud_n = Signal()
self.wr_n = Signal()
self.rd_n = Signal()
self.rst_n = Signal()
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class _TB(Module):
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def __init__(self):
pads = _TestPads()
self.submodules.dut = AD9858(pads, drive_fud=True)
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self.submodules.initiator = wishbone.Initiator(_test_gen())
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self.submodules.interconnect = wishbone.InterconnectPointToPoint(
self.initiator.bus, self.dut.bus)
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if __name__ == "__main__":
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run_simulation(_TB(), vcd_name="ad9858.vcd")