1 from nmigen
.compat
.sim
import run_simulation
2 from nmigen
.cli
import verilog
, rtlil
3 from nmigen
import Record
, Signal
, Module
, Const
, Elaboratable
, Mux
11 initial begin q=1'b0; q1=1'b1; end
15 {1'b0,1'b0}:begin q=q; q1=q1; end
16 {1'b0,1'b1}: begin q=1'b0; q1=1'b1; end
17 {1'b1,1'b0}:begin q=1'b1; q1=1'b0; end
18 {1'b1,1'b1}: begin q=~q; q1=~q1; end
25 def latchregister(m
, incoming
, outgoing
, settrue
, name
=None):
28 based on a conditon, "settrue", incoming data will be "latched"
29 into a register and passed out on "outgoing".
31 * if "settrue" is ASSERTED, outgoing is COMBINATORIALLY equal to incoming
32 * on the same cycle that settrue is DEASSERTED, outgoing REMAINS
33 equal (indefinitely) to the incoming value
35 # make reg same as input. reset OK.
36 if isinstance(incoming
, Record
):
37 reg
= Record
.like(incoming
, name
=name
)
39 reg
= Signal
.like(incoming
, name
=name
)
40 m
.d
.comb
+= outgoing
.eq(Mux(settrue
, incoming
, reg
))
41 with m
.If(settrue
): # pass in some kind of expression/condition here
42 m
.d
.sync
+= reg
.eq(incoming
) # latch input into register
45 def mkname(prefix
, suffix
):
48 return "%s_%s" % (prefix
, suffix
)
51 class SRLatch(Elaboratable
):
52 def __init__(self
, sync
=True, llen
=1, name
=None):
55 s_n
, r_n
= mkname("s", name
), mkname("r", name
)
56 q_n
, qn_n
= mkname("q", name
), mkname("qn", name
)
57 qlq_n
= mkname("qlq", name
)
58 self
.s
= Signal(llen
, name
=s_n
, reset
=0)
59 self
.r
= Signal(llen
, name
=r_n
, reset
=(1<<llen
)-1) # defaults to off
60 self
.q
= Signal(llen
, name
=q_n
, reset_less
=True)
61 self
.qn
= Signal(llen
, name
=qn_n
, reset_less
=True)
62 self
.qlq
= Signal(llen
, name
=qlq_n
, reset_less
=True)
64 def elaborate(self
, platform
):
66 q_int
= Signal(self
.llen
)
68 m
.d
.sync
+= q_int
.eq((q_int
& ~self
.r
) | self
.s
)
70 m
.d
.comb
+= self
.q
.eq(q_int
)
72 m
.d
.comb
+= self
.q
.eq((q_int
& ~self
.r
) | self
.s
)
73 m
.d
.comb
+= self
.qn
.eq(~self
.q
)
74 m
.d
.comb
+= self
.qlq
.eq(self
.q | q_int
) # useful output
79 return self
.s
, self
.r
, self
.q
, self
.qn
106 dut
= SRLatch(llen
=4)
107 vl
= rtlil
.convert(dut
, ports
=dut
.ports())
108 with
open("test_srlatch.il", "w") as f
:
111 run_simulation(dut
, sr_sim(dut
), vcd_name
='test_srlatch.vcd')
113 dut
= SRLatch(sync
=False, llen
=4)
114 vl
= rtlil
.convert(dut
, ports
=dut
.ports())
115 with
open("test_srlatch_async.il", "w") as f
:
118 run_simulation(dut
, sr_sim(dut
), vcd_name
='test_srlatch_async.vcd')
120 if __name__
== '__main__':