from nmigen.compat.sim import run_simulation
from nmigen.cli import verilog, rtlil
-from nmigen import Module, Signal, Elaboratable
+from nmigen import Module, Signal, Mux, Cat, Elaboratable
from nmutil.latch import SRLatch, latchregister
class LDSTCompUnit(Elaboratable):
+ """ LOAD / STORE / ADD / SUB Computation Unit
+
+ Inputs
+ ------
+
+ * :rwid: register width
+ * :alu: an ALU module
+ * :mem: a Memory Module (read-write capable)
+
+ Control Signals (In)
+ --------------------
+
+ * :issue_i: LD/ST is being "issued".
+ * :isalu_i: ADD/SUB is being "issued" (aka issue_alu_i)
+ * :shadown_i: Inverted-shadow is being held (stops STORE *and* WRITE)
+ * :go_rd_i: read is being actioned (latches in src regs)
+ * :go_ad_i: address is being actioned (triggers actual mem LD)
+ * :go_st_i: store is being actioned (triggers actual mem STORE)
+ * :go_die_i: resets the unit back to "wait for issue"
+ """
def __init__(self, rwid, opwid, alu, mem):
self.rwid = rwid
self.alu = alu
self.busy_o = Signal(reset_less=True) # fn busy out
self.rd_rel_o = Signal(reset_less=True) # request src1/src2
self.adr_rel_o = Signal(reset_less=True) # request address (from mem)
- self.sto_rel_o = Signal(reset_less=True) # request store (to mem)
+ self.sto_rel_o = Signal(reset_less=True) # request store (to mem)
self.req_rel_o = Signal(reset_less=True) # request write (result)
self.data_o = Signal(rwid, reset_less=True) # Dest out (LD or ALU)
self.load_mem_o = Signal(reset_less=True) # activate memory LOAD
def elaborate(self, platform):
m = Module()
+ comb = m.d.comb
+ sync = m.d.sync
+
m.submodules.alu = self.alu
m.submodules.src_l = src_l = SRLatch(sync=False)
m.submodules.opc_l = opc_l = SRLatch(sync=False)
m.submodules.sto_l = sto_l = SRLatch(sync=False)
# shadow/go_die
+ reset_b = Signal(reset_less=True)
reset_w = Signal(reset_less=True)
reset_a = Signal(reset_less=True)
reset_s = Signal(reset_less=True)
reset_r = Signal(reset_less=True)
- m.d.comb += reset_b.eq(self.go_st_ | self.go_wr_i | self.go_die_i)
- m.d.comb += reset_w.eq(self.go_wr_i | self.go_die_i)
- m.d.comb += reset_s.eq(self.go_st_i | self.go_die_i)
- m.d.comb += reset_r.eq(self.go_rd_i | self.go_die_i)
+ comb += reset_b.eq(self.go_st_i | self.go_wr_i | self.go_die_i)
+ comb += reset_w.eq(self.go_wr_i | self.go_die_i)
+ comb += reset_s.eq(self.go_st_i | self.go_die_i)
+ comb += reset_r.eq(self.go_rd_i | self.go_die_i)
# this one is slightly different, issue_alu_i selects go_wr_i)
a_sel = Mux(self.isalu_i, self.go_wr_i, self.go_ad_i )
- m.d.comb += reset_a.eq(a_sel| self.go_die_i)
+ comb += reset_a.eq(a_sel| self.go_die_i)
# opcode decode
op_alu = Signal(reset_less=True)
op_is_ld = Signal(reset_less=True)
op_is_st = Signal(reset_less=True)
+ op_ldst = Signal(reset_less=True)
op_is_imm = Signal(reset_less=True)
- m.d.comb += op_alu.eq(self.oper_i[0])
- m.d.comb += op_is_imm.eq(self.oper_i[1])
- m.d.comb += op_is_ld.eq(self.oper_i[2])
- m.d.comb += op_is_st.eq(self.oper_i[3])
- m.d.comb += self.load_mem_o.eq(op_is_ld & self.go_ad_i)
- m.d.comb += self.stwd_mem_o.eq(op_is_st & self.go_st_i)
+
+ comb += op_alu.eq(self.oper_i[0])
+ comb += op_is_imm.eq(self.oper_i[1])
+ comb += op_is_ld.eq(self.oper_i[2])
+ comb += op_is_st.eq(self.oper_i[3])
+ comb += op_ldst.eq(op_is_ld | op_is_st)
+ comb += self.load_mem_o.eq(op_is_ld & self.go_ad_i)
+ comb += self.stwd_mem_o.eq(op_is_st & self.go_st_i)
# select immediate or src2 reg to add
src2_or_imm = Signal(self.rwid, reset_less=True)
# issue can be either issue_i or issue_alu_i (isalu_i)
issue_i = Signal(reset_less=True)
- m.d.comb += issue_i.eq(self.issue_i | self.isalu_i)
+ comb += issue_i.eq(self.issue_i | self.isalu_i)
# Ripple-down the latches, each one set cancels the previous.
# NOTE: use sync to stop combinatorial loops.
# opcode latch - inverted so that busy resets to 0
- m.d.sync += opc_l.s.eq(issue_i) # XXX NOTE: INVERTED FROM book!
- m.d.sync += opc_l.r.eq(reset_b) # XXX NOTE: INVERTED FROM book!
+ sync += opc_l.s.eq(issue_i) # XXX NOTE: INVERTED FROM book!
+ sync += opc_l.r.eq(reset_b) # XXX NOTE: INVERTED FROM book!
# src operand latch
- m.d.sync += src_l.s.eq(issue_i)
- m.d.sync += src_l.r.eq(reset_r)
+ sync += src_l.s.eq(issue_i)
+ sync += src_l.r.eq(reset_r)
+
+ # addr latch
+ sync += adr_l.s.eq(self.go_rd_i)
+ sync += adr_l.r.eq(reset_a)
+
+ # dest operand latch
+ sync += req_l.s.eq(self.go_ad_i)
+ sync += req_l.r.eq(reset_w)
- # addr latch
- m.d.sync += req_l.s.eq(self.go_rd_i)
- m.d.sync += req_l.r.eq(reset_a)
+ # store latch
+ sync += sto_l.s.eq(self.go_ad_i)
+ sync += sto_l.r.eq(reset_s)
- # dest operand latch
- m.d.sync += req_l.s.eq(self.go_ad_i)
- m.d.sync += req_l.r.eq(reset_w)
+ # outputs: busy and release signals
+ busy_o = self.busy_o
+ comb += self.busy_o.eq(opc_l.q) # busy out
+ comb += self.rd_rel_o.eq(src_l.q & busy_o) # src1/src2 req rel
+ comb += self.sto_rel_o.eq(sto_l.q & busy_o & self.shadown_i)
- # dest operand latch
- m.d.sync += req_l.s.eq(self.go_ad_i)
- m.d.sync += req_l.r.eq(reset_s)
+ # address release only happens on LD/ST, and is shadowed.
+ comb += self.adr_rel_o.eq(adr_l.q & op_ldst & busy_o & self.shadownn_i)
- # outputs
- m.d.comb += self.busy_o.eq(opc_l.q) # busy out
- m.d.comb += self.rd_rel_o.eq(src_l.q & opc_l.q) # src1/src2 req rel
+ # request release enabled based on if op is a LD/ST or a plain ALU
+ # if op is a LD/ST, req_rel activates from the *address* latch
+ # if op is ADD/SUB, req_rel activates from the *dest* latch
+ wr_q = Signal(reset_less=True)
+ comb += wr_q.eq(Mux(op_ldst, adr_l.q, req_l.q))
# the counter is just for demo purposes, to get the ALUs of different
# types to take arbitrary completion times
with m.If(opc_l.qn):
- m.d.sync += self.counter.eq(0)
- with m.If(req_l.qn & opc_l.q & (self.counter == 0)):
- with m.If(self.oper_i == 2): # MUL, to take 5 instructions
- m.d.sync += self.counter.eq(5)
- with m.Elif(self.oper_i == 3): # SHIFT to take 7
- m.d.sync += self.counter.eq(7)
- with m.Else(): # ADD/SUB to take 2
- m.d.sync += self.counter.eq(2)
+ sync += self.counter.eq(0) # reset counter when not busy
+ with m.If(req_l.qn & busy_o & (self.counter == 0)):
+ sync += self.counter.eq(2) # take 2 (fake) cycles to respond
with m.If(self.counter > 1):
- m.d.sync += self.counter.eq(self.counter - 1)
+ sync += self.counter.eq(self.counter - 1)
with m.If(self.counter == 1):
# write req release out. waits until shadow is dropped.
- m.d.comb += self.req_rel_o.eq(req_l.q & opc_l.q & self.shadown_i)
+ comb += self.req_rel_o.eq(wr_q & busy_o & self.shadown_i)
# select immediate if opcode says so. however also change the latch
# to trigger *from* the opcode latch instead.
- m.d.comb += src_sel.eq(Mux(op_is_imm, opc_l.q, src_l.q))
- m.d.comb += src2_or_imm.eq(Mux(op_is_imm, self.imm_i, self.src2_i)
+ comb += src_sel.eq(Mux(op_is_imm, opc_l.qn, src_l.q))
+ comb += src2_or_imm.eq(Mux(op_is_imm, self.imm_i, self.src2_i))
# create a latch/register for src1/src2 (include immediate select)
latchregister(m, self.src1_i, self.alu.a, src_l.q)
latchregister(m, src2_or_imm, self.alu.b, src_sel)
# create a latch/register for the operand
- latchregister(m, self.oper_i, self.alu.op, self.issue_i)
+ latchregister(m, Cat(op_alu, 0), self.alu.op, self.issue_i)
# and one for the output from the ALU
data_r = Signal(self.rwid, reset_less=True) # Dest register
latchregister(m, self.alu.o, data_r, req_l.q)
with m.If(self.go_wr_i):
- m.d.comb += self.data_o.eq(data_r)
+ comb += self.data_o.eq(data_r)
return m
+ def __iter__(self):
+ yield self.go_rd_i
+ yield self.go_ad_i
+ yield self.go_wr_i
+ yield self.go_st_i
+ yield self.issue_i
+ yield self.isalu_i
+ yield self.shadown_i
+ yield self.go_die_i
+ yield self.oper_i
+ yield self.imm_i
+ yield self.src1_i
+ yield self.src2_i
+ yield self.busy_o
+ yield self.rd_rel_o
+ yield self.adr_rel_o
+ yield self.sto_rel_o
+ yield self.req_rel_o
+ yield self.data_o
+ yield self.load_mem_o
+ yield self.stwd_mem_o
+
+ def ports(self):
+ return list(self)
+
+
def scoreboard_sim(dut):
yield dut.dest_i.eq(1)
yield dut.issue_i.eq(1)
yield dut.go_write_i.eq(0)
yield
+
def test_scoreboard():
- dut = Scoreboard(32, 8)
+ from alu_hier import ALU
+ alu = ALU(16)
+ mem = alu # fake
+ dut = LDSTCompUnit(16, 4, alu, mem)
vl = rtlil.convert(dut, ports=dut.ports())
- with open("test_scoreboard.il", "w") as f:
+ with open("test_ldst_comp.il", "w") as f:
f.write(vl)
- run_simulation(dut, scoreboard_sim(dut), vcd_name='test_scoreboard.vcd')
+ run_simulation(dut, scoreboard_sim(dut), vcd_name='test_ldst_comp.vcd')
if __name__ == '__main__':
test_scoreboard()
projects / soc.git / blobdiff