Implement tRAS

litedram/common.py

@@ -43,7 +43,7 @@ class GeomSettings:
 
 
 class TimingSettings:
-    def __init__(self, tRP, tRCD, tWR, tWTR, tREFI, tRFC, tFAW, tCCD, tRRD, tRC):
+    def __init__(self, tRP, tRCD, tWR, tWTR, tREFI, tRFC, tFAW, tCCD, tRRD, tRC, tRAS):
         self.tRP = tRP
         self.tRCD = tRCD
         self.tWR = tWR
@@ -54,6 +54,7 @@ class TimingSettings:
         self.tCCD = tCCD
         self.tRRD = tRRD
         self.tRC = tRC
+        self.tRAS = tRAS
 
 
 def cmd_layout(address_width):

litedram/core/bankmachine.py

@@ -100,12 +100,23 @@ class BankMachine(Module):
         else:
             self.comb += activate_allowed.eq(1)
 
+        # Respect tRAS activate-precharge time
+        precharge_allowed = Signal()
+        if settings.timing.tRAS is not None:
+            tras_time = settings.timing.tRAS - 1
+            tras_timer = WaitTimer(tras_time)
+            self.submodules += tras_timer
+            self.comb += tras_timer.wait.eq(~(cmd.valid & cmd.ready & track_open))
+            self.comb += precharge_allowed.eq(tras_timer.done)
+        else:
+            self.comb += precharge_allowed.eq(1)
+
         # Auto Precharge
         if settings.with_auto_precharge:
             self.comb += [
                 If(cmd_buffer_lookahead.source.valid & cmd_buffer.source.valid,
                     If(slicer.row(cmd_buffer_lookahead.source.addr) != slicer.row(cmd_buffer.source.addr),
-                        auto_precharge.eq((track_close == 0))
+                        auto_precharge.eq((track_close == 0) & precharge_allowed)
                     )
                 )
             ]
@@ -144,7 +155,7 @@ class BankMachine(Module):
         )
         fsm.act("PRECHARGE",
             # Note: we are presenting the column address, A10 is always low
-            If(precharge_timer.done,
+            If(precharge_timer.done & precharge_allowed,
                 cmd.valid.eq(1),
                 If(cmd.ready,
                     NextState("TRP")

litedram/modules.py

@@ -35,7 +35,8 @@ class SDRAMModule:
             tFAW=None if self.get("tFAW") is None else self.ck_ns_to_cycles(*self.get("tFAW")),
             tCCD=None if self.get("tCCD") is None else self.ck_ns_to_cycles(*self.get("tCCD")),
             tRRD=None if self.get("tRRD") is None else self.ns_to_cycles_trrd(self.get("tRRD")),
-            tRC=None if self.get("tRC") is None else self.ns_to_cycles(self.get("tRC"))
+            tRC=None if self.get("tRC") is None else self.ns_to_cycles(self.get("tRC")),
+            tRAS=None if self.get("tRAS") is None else self.ns_to_cycles(self.get("tRAS"))
         )
 
     def get(self, name):
@@ -254,6 +255,7 @@ class MT41J128M16(SDRAMModule):
     tRFC_1066 = 86
     tFAW_1066 = (27, None)
     tRC_1066 = 50.625
+    tRAS_1066 = 37.5
     # DDR3-1333
     tRP_1333  = 13.5
     tRCD_1333 = 13.5
@@ -261,6 +263,7 @@ class MT41J128M16(SDRAMModule):
     tRFC_1333 = 107
     tFAW_1333 = (30, None)
     tRC_1333 = 49.5
+    tRAS_1333 = 36
     # DDR3-1600
     tRP_1600  = 13.75
     tRCD_1600 = 13.75
@@ -268,6 +271,7 @@ class MT41J128M16(SDRAMModule):
     tRFC_1600 = 128
     tFAW_1600 = (32, None)
     tRC_1600 = 48.75
+    tRAS_1600 = 35
     # API retro-compatibility
     tRP  = tRP_1600
     tRCD = tRCD_1600
@@ -275,6 +279,7 @@ class MT41J128M16(SDRAMModule):
     tRFC = tRFC_1600
     tFAW = tFAW_1600
     tRC = tRC_1600
+    tRAS = tRAS_1600
 
 
 class MT41K128M16(MT41J128M16):