litex/misoc/cores/lasmicon/refresher.py

71 lines
2.1 KiB
Python

from migen import *
from migen.genlib.misc import timeline
from migen.genlib.fsm import FSM
from misoc.mem.sdram.core.lasmicon.multiplexer import *
class Refresher(Module):
def __init__(self, a, ba, tRP, tREFI, tRFC, enabled=True):
self.req = Signal()
self.ack = Signal() # 1st command 1 cycle after assertion of ack
self.cmd = CommandRequest(a, ba)
###
if enabled:
# Refresh sequence generator:
# PRECHARGE ALL --(tRP)--> AUTO REFRESH --(tRFC)--> done
seq_start = Signal()
seq_done = Signal()
self.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)
]
self.sync += timeline(seq_start, [
(1, [
self.cmd.ras_n.eq(0),
self.cmd.we_n.eq(0)
]),
(1+tRP, [
self.cmd.cas_n.eq(0),
self.cmd.ras_n.eq(0)
]),
(1+tRP+tRFC, [
seq_done.eq(1)
])
])
# Periodic refresh counter
counter = Signal(max=tREFI)
start = Signal()
self.sync += [
start.eq(0),
If(counter == 0,
start.eq(1),
counter.eq(tREFI - 1)
).Else(
counter.eq(counter - 1)
)
]
# Control FSM
fsm = FSM()
self.submodules += fsm
fsm.act("IDLE", If(start, NextState("WAIT_GRANT")))
fsm.act("WAIT_GRANT",
self.req.eq(1),
If(self.ack,
seq_start.eq(1),
NextState("WAIT_SEQ")
)
)
fsm.act("WAIT_SEQ",
self.req.eq(1),
If(seq_done, NextState("IDLE"))
)