add (but comment out) reset signal

[ieee754fpu.git] / src / add / example_buf_pipe.py

diff --git a/src/add/example_buf_pipe.py b/src/add/example_buf_pipe.py
index 20e91e4e877948f72000b5ac789b053f82d21f4d..b72e1c43904451ba0ef7f9fa78d5417da8de0a8d 100644 (file)
--- a/src/add/example_buf_pipe.py
+++ b/src/add/example_buf_pipe.py
@@ -1,3 +1,6 @@
+""" nmigen implementation of buffered pipeline stage, based on zipcpu:
+    https://zipcpu.com/blog/2017/08/14/strategies-for-pipelining.html
+"""
 from nmigen import Signal, Cat, Const, Mux, Module
 from nmigen.compat.sim import run_simulation
 from nmigen.cli import verilog, rtlil
@@ -5,6 +8,7 @@ from nmigen.cli import verilog, rtlil
 class BufPipe:
     def __init__(self):
         # input
+        #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_data = Signal(32) # >>in - comes in from the PREVIOUS stage
@@ -19,7 +23,7 @@ class BufPipe:
         self.o_data = Signal(32) # out>> - goes out to the NEXT stage
 
     def pre_process(self, d_in):
-        return d_in
+        return d_in | 0xf0000
 
     def process(self, d_in):
         return d_in + 1
@@ -30,6 +34,9 @@ class BufPipe:
         i_p_stb_o_p_busyn = Signal(reset_less=True)
         m.d.comb += i_p_stb_o_p_busyn.eq(self.i_p_stb & (~self.o_p_busy))
 
+        #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_n_busy): # previous stage is not busy
             with m.If(~self.o_p_busy): # not stalled
                 # nothing in buffer: send input direct to output
@@ -71,6 +78,13 @@ class BufPipe:
 
 
 def testbench(dut):
+    #yield dut.i_p_rst.eq(1)
+    yield dut.i_n_busy.eq(1)
+    yield dut.o_p_busy.eq(1)
+    yield
+    yield
+    #yield dut.i_p_rst.eq(0)
+    yield dut.i_n_busy.eq(0)
     yield dut.i_data.eq(5)
     yield dut.i_p_stb.eq(1)
     yield