forked from M-Labs/artiq
183 lines
5.0 KiB
Python
183 lines
5.0 KiB
Python
from migen import *
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from migen.genlib.fsm import *
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from migen.genlib.misc import WaitTimer
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from misoc.interconnect import wishbone
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class AD9xxx(Module):
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"""Wishbone interface to the AD9858 and AD9914 DDS chips.
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Addresses 0-2**len(pads.a)-1 map the AD9xxx registers.
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Write to address 2**len(pads.a) to pulse the FUD signal.
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Address 2**len(pads.a)+1 is a GPIO register that controls the
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sel and reset signals. rst is mapped to bit 0, followed by sel.
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Write timing:
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Address is set one cycle before assertion of we_n.
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we_n is asserted for one cycle, at the same time as valid data is driven.
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Read timing:
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Address is set one cycle before assertion of rd_n.
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rd_n is asserted for read_wait_cycles, data is sampled at the end.
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rd_n is deasserted and data bus is not driven again before hiz_wait_cycles.
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Design:
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All IO pads are registered.
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"""
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def __init__(self, pads,
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read_wait_cycles=10, hiz_wait_cycles=3,
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bus=None):
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if bus is None:
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bus = wishbone.Interface(data_width=len(pads.d))
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self.bus = bus
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# # #
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dts = TSTriple(len(pads.d))
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self.specials += dts.get_tristate(pads.d)
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hold_address = Signal()
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dr = Signal(len(pads.d))
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rx = Signal()
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self.sync += [
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If(~hold_address, pads.a.eq(bus.adr)),
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dts.o.eq(bus.dat_w),
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dr.eq(dts.i),
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dts.oe.eq(~rx)
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]
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if hasattr(pads, "sel"):
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sel_len = len(pads.sel)
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else:
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sel_len = len(pads.sel_n)
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gpio = Signal(sel_len + 1)
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gpio_load = Signal()
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self.sync += If(gpio_load, gpio.eq(bus.dat_w))
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if hasattr(pads, "rst"):
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self.comb += pads.rst.eq(gpio[0])
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else:
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self.comb += pads.rst_n.eq(~gpio[0])
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if hasattr(pads, "sel"):
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self.comb += pads.sel.eq(gpio[1:])
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else:
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self.comb += pads.sel_n.eq(~gpio[1:])
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bus_r_gpio = Signal()
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self.comb += If(bus_r_gpio,
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bus.dat_r.eq(gpio)
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).Else(
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bus.dat_r.eq(dr)
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)
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fud = Signal()
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if hasattr(pads, "fud"):
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self.sync += pads.fud.eq(fud)
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else:
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self.sync += pads.fud_n.eq(~fud)
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pads.wr_n.reset = 1
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pads.rd_n.reset = 1
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wr = Signal()
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rd = Signal()
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self.sync += pads.wr_n.eq(~wr), pads.rd_n.eq(~rd)
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self.submodules.read_timer = WaitTimer(read_wait_cycles)
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self.submodules.hiz_timer = WaitTimer(hiz_wait_cycles)
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fsm = FSM("IDLE")
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self.submodules += fsm
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fsm.act("IDLE",
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If(bus.cyc & bus.stb,
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If(bus.adr[len(pads.a)],
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If(bus.adr[0],
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NextState("GPIO")
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).Else(
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NextState("FUD")
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)
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).Else(
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If(bus.we,
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NextState("WRITE")
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).Else(
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NextState("READ")
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)
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)
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)
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)
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fsm.act("WRITE",
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# 3ns A setup to WR active
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wr.eq(1),
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NextState("WRITE0")
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)
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fsm.act("WRITE0",
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# 3.5ns D setup to WR inactive
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# 0ns D and A hold to WR inactive
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bus.ack.eq(1),
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NextState("IDLE")
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)
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fsm.act("READ",
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# 15ns D valid to A setup
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# 15ns D valid to RD active
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rx.eq(1),
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rd.eq(1),
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self.read_timer.wait.eq(1),
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If(self.read_timer.done,
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bus.ack.eq(1),
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NextState("WAIT_HIZ")
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)
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)
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fsm.act("WAIT_HIZ",
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rx.eq(1),
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# For some reason, AD9858 has an address hold time to RD inactive.
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hold_address.eq(1),
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self.hiz_timer.wait.eq(1),
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If(self.hiz_timer.done, NextState("IDLE"))
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)
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fsm.act("FUD",
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# 4ns FUD setup to SYNCLK
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# 0ns FUD hold to SYNCLK
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fud.eq(1),
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bus.ack.eq(1),
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NextState("IDLE")
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)
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fsm.act("GPIO",
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bus.ack.eq(1),
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bus_r_gpio.eq(1),
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If(bus.we, gpio_load.eq(1)),
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NextState("IDLE")
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)
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def _test_gen(bus):
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# Test external bus writes
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yield from bus.write(4, 2)
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yield from bus.write(5, 3)
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yield
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# Test external bus reads
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yield from bus.read(14)
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yield from bus.read(15)
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yield
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# Test FUD
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yield from bus.write(64, 0)
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yield
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# Test GPIO
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yield from bus.write(65, 0xff)
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yield
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class _TestPads:
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def __init__(self):
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self.a = Signal(6)
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self.d = Signal(8)
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self.sel = Signal(5)
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self.fud_n = Signal()
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self.wr_n = Signal()
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self.rd_n = Signal()
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self.rst_n = Signal()
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if __name__ == "__main__":
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pads = _TestPads()
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dut = AD9xxx(pads)
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run_simulation(dut, _test_gen(dut.bus), vcd_name="ad9xxx.vcd")
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