def test():
datawid = vast.Parameter( 'DATAWID', vast.Rvalue(vast.IntConst('32')) )
params = vast.Paramlist( [datawid] )
clk = vast.Ioport( vast.Input('CLK') )
rst = vast.Ioport( vast.Input('RST') )
width = vast.Width( vast.IntConst('7'), vast.IntConst('0') )
led = vast.Ioport( vast.Output('led', width=width) )
ports = vast.Portlist( [clk, rst, led] )
width = vast.Width( vast.Minus(vast.Identifier('DATAWID'), vast.IntConst('1')), vast.IntConst('0') )
count = vast.Reg('count', width=width)
assign = vast.Assign(
vast.Lvalue(vast.Identifier('led')),
vast.Rvalue(
vast.Partselect(
vast.Identifier('count'), # count
vast.Minus(vast.Identifier('DATAWID'), vast.IntConst('1')), # [DATAWID-1:
vast.Minus(vast.Identifier('DATAWID'), vast.IntConst('8'))))) # :DATAWID-8]
sens = vast.Sens(vast.Identifier('CLK'), type='posedge')
senslist = vast.SensList([ sens ])
assign_count_true = vast.NonblockingSubstitution(
vast.Lvalue(vast.Identifier('count')),
vast.Rvalue(vast.IntConst('0')))
if0_true = vast.Block([ assign_count_true ])
# (count + 1) * 2
count_plus_1 = vast.Plus(vast.Identifier('count'), vast.IntConst('1'))
cp1_times_2 = vast.Times(count_plus_1, vast.IntConst('2'))
cp1t2_plus_1 = vast.Plus(cp1_times_2, vast.IntConst('1'))
assign_count_false = vast.NonblockingSubstitution(
vast.Lvalue(vast.Identifier('count')),
vast.Rvalue(cp1t2_plus_1))
if0_false = vast.Block([ assign_count_false ])
if0 = vast.IfStatement(vast.Identifier('RST'), if0_true, if0_false)
statement = vast.Block([ if0 ])
always = vast.Always(senslist, statement)
items = []
items.append(count)
items.append(assign)
items.append(always)
ast = vast.ModuleDef("top", params, ports, items)
codegen = ASTCodeGenerator()
rslt = codegen.visit(ast)
print(rslt)
assert(expected == rslt)
def gen_lat(path):
clk = vast.Ioport(vast.Input('en'))
q = vast.Ioport(vast.Output('Q'))
d = vast.Ioport(vast.Input('D'))
r = vast.Ioport(vast.Input('rst'))
ports = vast.Portlist([clk, q, d, r])
q_reg = vast.Identifier('reg Q = 0;')
sens = []
sens.append(vast.Sens(vast.Identifier('en'), type='level'))
sens.append(vast.Sens(vast.Identifier('rst'), type='level'))
sens.append(vast.Sens(vast.Identifier('D'), type='level'))
senslist = vast.SensList(sens)
assign_q = vast.NonblockingSubstitution(vast.Lvalue(vast.Identifier('Q')),
vast.Rvalue(vast.Identifier('D')))
blocks = []
blocks.append(
vast.IfStatement(
vast.Identifier('rst'), vast.Identifier('Q <= 0;'),
vast.IfStatement(vast.Identifier('en'), assign_q, None), None))
statement = vast.Block(blocks)
always = vast.Always(senslist, statement)
items = []
items.append(q_reg)
items.append(always)
ast = vast.ModuleDef("lat", None, ports, items)
write_verilog(ast, 'lat.v', path)
def lower_action(fsm_reg: vast.Reg, done_stage: vast.IntConst, action: Action):
body = [lower_update(upd) for upd in action.updates]
# Statement to update the FSM register to next state.
st_upd = vast.NonblockingSubstitution(
vast.Lvalue(vast.Identifier(fsm_reg.name)),
lower_next(done_stage, action.next_state),
)
return vast.Block(body + [st_upd])
def visit_Subst(self, node):
left = self.visit(node.left)
right = self.visit(node.right)
ldelay = self.visit(node.ldelay) if node.ldelay else None
rdelay = self.visit(node.rdelay) if node.rdelay else None
lvalue = vast.Lvalue(left)
rvalue = vast.Rvalue(right)
if node.blk:
return vast.BlockingSubstitution(lvalue, rvalue, ldelay, rdelay)
return vast.NonblockingSubstitution(lvalue, rvalue, ldelay, rdelay)
def gen_dff(path):
clk = vast.Ioport(vast.Input('clk'))
q = vast.Ioport(vast.Output('Q'))
d = vast.Ioport(vast.Input('D'))
ports = vast.Portlist([clk, q, d])
q_reg = vast.Identifier('reg Q = 0;')
sens = vast.Sens(vast.Identifier('clk'), type='posedge')
senslist = vast.SensList([sens])
assign_q = vast.NonblockingSubstitution(vast.Lvalue(vast.Identifier('Q')),
vast.Rvalue(vast.Identifier('D')))
statement = vast.Block([assign_q])
always = vast.Always(senslist, statement)
items = []
items.append(q_reg)
items.append(always)
ast = vast.ModuleDef("dff", None, ports, items)
write_verilog(ast, 'dff.v', path)
def lower_fsm(fsm: FSM):
assert fsm.start_state == 0, "Starting state is not 0"
zero = vast.IntConst(0)
all_registers = [
Register("a", 8),
Register("b", 8),
Register("tmp", 8),
Register("_cond", 1),
]
register_defs = [
vast.Reg(
reg.name,
vast.Width(vast.IntConst(reg.width -
1), zero) if reg.width - 1 != 0 else None)
for reg in all_registers
]
ports = vast.Portlist([
vast.Ioport(vast.Input('clk')),
# XXX(rachit): AST can't represent `output reg done`
# so assign to a local register and use a wire.
vast.Ioport(vast.Output('done')),
])
done_state = max(fsm.actions.keys()) + 1
done_reg = vast.Reg('done_out')
hook_up_done = vast.Assign(
vast.Lvalue(vast.Identifier('done')),
vast.Rvalue(vast.Identifier('done_out')),
)
# Register to store the FSM state.
fsm_reg_size = int(math.ceil(math.log2(done_state))) + 1
fsm_reg = vast.Reg(name="fsm_reg",
width=vast.Width(vast.IntConst(fsm_reg_size - 1), zero))
# Define all the registers.
reg_decl = register_defs + [fsm_reg]
# Define the initial process
inits = vast.Initial(
vast.Block([
vast.BlockingSubstitution(
vast.Lvalue(vast.Identifier(reg.name)),
vast.Rvalue(vast.IntConst(0)),
) for reg in reg_decl
]))
# Default case, assigns to the done register.
done = vast.IntConst(done_state)
default_case = vast.Case(cond=None,
statement=vast.Block([
vast.NonblockingSubstitution(
vast.Lvalue(vast.Identifier(reg.name)),
vast.Rvalue(vast.Identifier(reg.name)),
) for reg in reg_decl
] + [
vast.NonblockingSubstitution(
vast.Lvalue(vast.Identifier('done_out')),
vast.Rvalue(vast.IntConst(1)))
]))
# Generate Case conditions for each transition.
cases = [
vast.Case([vast.IntConst(cond_val)],
lower_action(fsm_reg, done, action))
for (cond_val, action) in fsm.actions.items()
]
case_statement = vast.CaseStatement(comp=vast.Identifier(fsm_reg.name),
caselist=cases + [default_case])
always_ff = vast.Always(
vast.SensList([vast.Sens(vast.Identifier('clk'), 'posedge')]),
vast.Block([case_statement]))
return vast.ModuleDef(name="main",
paramlist=vast.Paramlist([]),
portlist=ports,
items=reg_decl +
[done_reg, hook_up_done, inits, always_ff])
def lower_update(upd: Update):
reg = upd.register.name
return vast.NonblockingSubstitution(vast.Lvalue(vast.Identifier(reg)),
vast.Rvalue(lower_expr(upd.expr)))