from migen.fhdl.structure import * from migen.corelogic.misc import timeline from migen.corelogic.fsm import FSM from milkymist.asmicon.multiplexer import * class Refresher: def __init__(self, a, ba, tRP, tREFI, tRFC): self.tRP = tRP self.tREFI = tREFI self.tRFC = tRFC self.req = Signal() self.ack = Signal() # 1st command 1 cycle after assertion of ack self.cmd = CommandRequest(a, ba) def get_fragment(self): comb = [] sync = [] # Refresh sequence generator: # PRECHARGE ALL --(tRP)--> AUTO REFRESH --(tRFC)--> done seq_start = Signal() seq_done = Signal() sync += [ self.cmd.a.eq(2**10), self.cmd.ba.eq(0), self.cmd.cas_n.eq(1), self.cmd.ras_n.eq(1), self.cmd.we_n.eq(1), seq_done.eq(0) ] sync += timeline(seq_start, [ (1, [ self.cmd.ras_n.eq(0), self.cmd.we_n.eq(0) ]), (1+self.tRP, [ self.cmd.cas_n.eq(0), self.cmd.ras_n.eq(0) ]), (1+self.tRP+self.tRFC, [ seq_done.eq(1) ]) ]) # Periodic refresh counter counter = Signal(max=self.tREFI) start = Signal() sync += [ start.eq(0), If(counter == 0, start.eq(1), counter.eq(self.tREFI - 1) ).Else( counter.eq(counter - 1) ) ] # Control FSM fsm = FSM("IDLE", "WAIT_GRANT", "WAIT_SEQ") fsm.act(fsm.IDLE, If(start, fsm.next_state(fsm.WAIT_GRANT))) fsm.act(fsm.WAIT_GRANT, self.req.eq(1), If(self.ack, seq_start.eq(1), fsm.next_state(fsm.WAIT_SEQ) ) ) fsm.act(fsm.WAIT_SEQ, self.req.eq(1), If(seq_done, fsm.next_state(fsm.IDLE)) ) return Fragment(comb, sync) + fsm.get_fragment()