where data will flow on *every* clock when the conditions are right.
input acceptance conditions are when:
- * incoming previous-stage strobe (i_p_stb) is HIGH
- * outgoing previous-stage busy (o_p_busy) is LOW
+ * incoming previous-stage strobe (i.p_stb) is HIGH
+ * outgoing previous-stage busy (o.p_busy) is LOW
output transmission conditions are when:
- * outgoing next-stage strobe (o_n_stb) is HIGH
- * outgoing next-stage busy (i_n_busy) is LOW
+ * outgoing next-stage strobe (o.n_stb) is HIGH
+ * outgoing next-stage busy (i.n_busy) is LOW
the tricky bit is when the input has valid data and the output is not
ready to accept it. if it wasn't for the clock synchronisation, it
def ports(self):
return [self.i_data, self.o_data]
+class IOAckIn:
+
+ def __init__(self):
+ self.p_stb = Signal() # >>in - comes in from PREVIOUS stage
+ self.n_busy = Signal() # in<< - comes in from the NEXT stage
+
+
+class IOAckOut:
+
+ def __init__(self):
+ self.n_stb = Signal() # out>> - goes out to the NEXT stage
+ self.p_busy = Signal() # <<out - goes out to the PREVIOUS stage
+
class BufferedPipeline:
""" buffered pipeline stage
- stage-1 i_p_stb >>in stage o_n_stb out>> stage+1
- stage-1 o_p_busy <<out stage i_n_busy <<in stage+1
+ stage-1 i.p_stb >>in stage o.n_stb out>> stage+1
+ stage-1 o.p_busy <<out stage i.n_busy <<in stage+1
stage-1 i_data >>in stage o_data out>> stage+1
| |
+-------> process
"""
def __init__(self):
# input: strobe comes in from previous stage, busy comes in from next
- #self.i_p_rst = Signal() # >>in - comes in from PREVIOUS stage
- self.i_p_stb = Signal() # >>in - comes in from PREVIOUS stage
- self.i_n_busy = Signal() # in<< - comes in from the NEXT stage
+ self.i = IOAckIn()
+ #self.i.p_stb = Signal() # >>in - comes in from PREVIOUS stage
+ #self.i.n_busy = Signal() # in<< - comes in from the NEXT stage
# output: strobe goes out to next stage, busy comes in from previous
- self.o_n_stb = Signal() # out>> - goes out to the NEXT stage
- self.o_p_busy = Signal() # <<out - goes out to the PREVIOUS stage
+ self.o = IOAckOut()
+ #self.o.n_stb = Signal() # out>> - goes out to the NEXT stage
+ #self.o.p_busy = Signal() # <<out - goes out to the PREVIOUS stage
def elaborate(self, platform):
m = Module()
o_n_stbn = Signal(reset_less=True)
i_n_busyn = Signal(reset_less=True)
i_p_stb_o_p_busyn = Signal(reset_less=True)
- m.d.comb += [i_n_busyn.eq(~self.i_n_busy),
- o_n_stbn.eq(~self.o_n_stb),
- o_p_busyn.eq(~self.o_p_busy),
- i_p_stb_o_p_busyn.eq(self.i_p_stb & o_p_busyn),
+ m.d.comb += [i_n_busyn.eq(~self.i.n_busy),
+ o_n_stbn.eq(~self.o.n_stb),
+ o_p_busyn.eq(~self.o.p_busy),
+ i_p_stb_o_p_busyn.eq(self.i.p_stb & o_p_busyn),
]
# store result of processing in combinatorial temporary
- with m.If(self.i_p_stb): # input is valid: process it
+ with m.If(self.i.p_stb): # input is valid: process it
m.d.comb += self.stage.process()
# if not in stall condition, update the temporary register
with m.If(o_p_busyn): # not stalled
m.d.sync += self.stage.update_buffer()
- #with m.If(self.i_p_rst): # reset
- # m.d.sync += self.o_n_stb.eq(0)
- # m.d.sync += self.o_p_busy.eq(0)
+ #with m.If(self.i.p_rst): # reset
+ # m.d.sync += self.o.n_stb.eq(0)
+ # m.d.sync += self.o.p_busy.eq(0)
with m.If(i_n_busyn): # next stage is not busy
with m.If(o_p_busyn): # not stalled
# nothing in buffer: send (processed) input direct to output
- m.d.sync += [self.o_n_stb.eq(self.i_p_stb),
+ m.d.sync += [self.o.n_stb.eq(self.i.p_stb),
self.stage.update_output(),
]
- with m.Else(): # o_p_busy is true, and something is in our buffer.
+ with m.Else(): # o.p_busy is true, and something is in our buffer.
# Flush the [already processed] buffer to the output port.
- m.d.sync += [self.o_n_stb.eq(1),
+ m.d.sync += [self.o.n_stb.eq(1),
self.stage.flush_buffer(),
# clear stall condition, declare register empty.
- self.o_p_busy.eq(0),
+ self.o.p_busy.eq(0),
]
- # ignore input, since o_p_busy is also true.
+ # ignore input, since o.p_busy is also true.
- # (i_n_busy) is true here: next stage is busy
+ # (i.n_busy) is true here: next stage is busy
with m.Elif(o_n_stbn): # next stage being told "not busy"
- m.d.sync += [self.o_n_stb.eq(self.i_p_stb),
- self.o_p_busy.eq(0), # Keep the buffer empty
+ m.d.sync += [self.o.n_stb.eq(self.i.p_stb),
+ self.o.p_busy.eq(0), # Keep the buffer empty
# set the output data (from comb result)
self.stage.update_output(),
]
- # (i_n_busy) and (o_n_stb) both true:
+ # (i.n_busy) and (o.n_stb) both true:
with m.Elif(i_p_stb_o_p_busyn):
# If next stage *is* busy, and not stalled yet, accept input
- m.d.sync += self.o_p_busy.eq(self.i_p_stb & self.o_n_stb)
+ m.d.sync += self.o.p_busy.eq(self.i.p_stb & self.o.n_stb)
return m
def ports(self):
- return [self.i_p_stb, self.i_n_busy,
- self.o_n_stb, self.o_p_busy,
+ return [self.i.p_stb, self.i.n_busy,
+ self.o.n_stb, self.o.p_busy,
]
projects / ieee754fpu.git / blobdiff