wrpll: add DDMTD cores

Author: sbourdeauducq

artiq/firmware/libboard_artiq/wrpll.rs

@@ -281,6 +281,15 @@ pub fn init() {
 
     clock::spin_us(10_000); // Settling Time after FS Change
     unsafe { csr::wrpll::helper_reset_write(0); }
+
+    info!("DDMTD test:");
+    for _ in 0..20 {
+        unsafe {
+            csr::wrpll::ddmtd_main_arm_write(1);
+            while csr::wrpll::ddmtd_main_arm_read() != 0 {}
+            info!("{}", csr::wrpll::ddmtd_main_tag_read());
+        }
+    }
 }
 
 pub fn select_recovered_clock(rc: bool) {

artiq/gateware/drtio/wrpll/core.py

@@ -3,10 +3,11 @@
 from misoc.interconnect.csr import *
 
 from artiq.gateware.drtio.wrpll.si549 import Si549
+from artiq.gateware.drtio.wrpll.ddmtd import DDMTD
 
 
 class WRPLL(Module, AutoCSR):
-    def __init__(self, helper_clk_pads, main_dcxo_i2c, helper_dxco_i2c):
+    def __init__(self, helper_clk_pads, main_dcxo_i2c, helper_dxco_i2c, ddmtd_inputs, N=15):
         self.helper_reset = CSRStorage(reset=1)
 
         self.clock_domains.cd_helper = ClockDomain()
@@ -19,3 +20,6 @@ def __init__(self, helper_clk_pads, main_dcxo_i2c, helper_dxco_i2c):
 
         self.submodules.main_dcxo = Si549(main_dcxo_i2c)
         self.submodules.helper_dcxo = Si549(helper_dxco_i2c)
+
+        self.submodules.ddmtd_helper = DDMTD(N, ddmtd_inputs.rec_clk)
+        self.submodules.ddmtd_main = DDMTD(N, ddmtd_inputs.main_xo)

artiq/gateware/drtio/wrpll/ddmtd.py

@@ -0,0 +1,62 @@
+from migen import *
+from migen.genlib.cdc import PulseSynchronizer, MultiReg
+from misoc.interconnect.csr import *
+
+
+class DDMTDEdgeDetector(Module):
+    def __init__(self, i):
+        self.rising = Signal()
+
+        history = Signal(4)
+        deglitched = Signal()
+        self.sync.helper += history.eq(Cat(history[1:], i))
+        self.comb += deglitched.eq(i | history[0] | history[1] | history[2] | history[3])
+
+        deglitched_r = Signal()
+        self.sync.helper += [
+            deglitched_r.eq(deglitched),
+            self.rising.eq(deglitched & ~deglitched_r)
+        ]
+
+
+class DDMTD(Module, AutoCSR):
+    def __init__(self, N, i):
+        self.arm = CSR()
+        self.tag = CSRStatus(N)
+
+        # in helper clock domain
+        self.h_tag = Signal(N)
+        self.h_tag_update = Signal()
+
+        # # #
+
+        ed = DDMTDEdgeDetector(i)
+        self.submodules += ed
+
+        counter = Signal(N)
+        self.sync.helper += [
+            counter.eq(counter + 1),
+            self.h_tag_update.eq(0),
+            If(ed.rising,
+                self.h_tag_update.eq(1),
+                self.h_tag.eq(counter)
+            )
+        ]
+
+        tag_update_ps = PulseSynchronizer("helper", "sys")
+        self.submodules += tag_update_ps
+        self.comb += tag_update_ps.i.eq(self.h_tag_update)
+        tag_update = Signal()
+        self.sync += tag_update.eq(tag_update_ps.o)
+
+        tag = Signal(N)
+        self.h_tag.attr.add("no_retiming")
+        self.specials += MultiReg(self.h_tag, tag)
+
+        self.sync += [
+            If(self.arm.re & self.arm.r, self.arm.w.eq(1)),
+            If(tag_update,
+                If(self.arm.w, self.tag.status.eq(tag)),
+                self.arm.w.eq(0),
+            )
+        ]

artiq/gateware/targets/sayma_amc.py

@@ -139,7 +139,8 @@ def __init__(self, rtio_clk_freq=125e6, identifier_suffix="", *, with_wrpll, **k
             self.submodules.wrpll = WRPLL(
                 helper_clk_pads=platform.request("ddmtd_helper_clk"),
                 main_dcxo_i2c=platform.request("ddmtd_main_dcxo_i2c"),
-                helper_dxco_i2c=platform.request("ddmtd_helper_dcxo_i2c"))
+                helper_dxco_i2c=platform.request("ddmtd_helper_dcxo_i2c"),
+                ddmtd_inputs=platform.request("ddmtd_inputs"))
             self.csr_devices.append("wrpll")
         else:
             self.comb += platform.request("filtered_clk_sel").eq(1)