3 files changed, 159 insertions, 11 deletions

diff --git a/hdl/clock.sv b/hdl/clock.sv
new file mode 100644
index 0000000..b33645b
--- /dev/null
+++ b/hdl/clock.sv
@@ -0,0 +1,140 @@
+`include "util.svh"
+
+module clock
+    #(  DIVIDE_BY   = 1
+    ,   MULTIPLY_BY = 1
+    ,   NATIVE_PERIOD_PICOSECONDS = 20_000
+    )
+    (   input   bit native_clk
+    ,   input   bit reset_n
+
+    ,   output  bit target_clk
+    ,   output  bit reset
+    );
+
+enum
+    {   AWAIT_LOCKED
+    ,   AWAIT_LOW
+    ,   AWAIT_HIGH
+    ,   AWAIT_LOW_2
+    ,   READY
+    } state = state.first;
+
+bit locked;
+
+`ifdef SYNTHESIS
+
+altpll
+    #(  .bandwidth_type("AUTO")
+    ,   .clk0_divide_by(DIVIDE_BY)
+    ,   .clk0_duty_cycle(50)
+    ,   .clk0_multiply_by(MULTIPLY_BY)
+    ,   .clk0_phase_shift(0)
+    ,   .compensate_clock("CLK0")
+    ,   .inclk0_input_frequency(NATIVE_PERIOD_PICOSECONDS)
+    ,   .intended_device_family("Cyclone 10 LP")
+    ,   .lpm_hint("CBX_MODULE_PREFIX=clock")
+    ,   .lpm_type("altpll")
+    ,   .operation_mode("NORMAL")
+    ,   .pll_type("AUTO")
+    ,   .port_activeclock("PORT_UNUSED")
+    ,   .port_areset("PORT_USED")
+    ,   .port_clkbad0("PORT_UNUSED")
+    ,   .port_clkbad1("PORT_UNUSED")
+    ,   .port_clkloss("PORT_UNUSED")
+    ,   .port_clkswitch("PORT_UNUSED")
+    ,   .port_configupdate("PORT_UNUSED")
+    ,   .port_fbin("PORT_UNUSED")
+    ,   .port_inclk0("PORT_USED")
+    ,   .port_inclk1("PORT_UNUSED")
+    ,   .port_locked("PORT_USED")
+    ,   .port_pfdena("PORT_UNUSED")
+    ,   .port_phasecounterselect("PORT_UNUSED")
+    ,   .port_phasedone("PORT_UNUSED")
+    ,   .port_phasestep("PORT_UNUSED")
+    ,   .port_phaseupdown("PORT_UNUSED")
+    ,   .port_pllena("PORT_UNUSED")
+    ,   .port_scanaclr("PORT_UNUSED")
+    ,   .port_scanclk("PORT_UNUSED")
+    ,   .port_scanclkena("PORT_UNUSED")
+    ,   .port_scandata("PORT_UNUSED")
+    ,   .port_scandataout("PORT_UNUSED")
+    ,   .port_scandone("PORT_UNUSED")
+    ,   .port_scanread("PORT_UNUSED")
+    ,   .port_scanwrite("PORT_UNUSED")
+    ,   .port_clk0("PORT_USED")
+    ,   .port_clk1("PORT_UNUSED")
+    ,   .port_clk2("PORT_UNUSED")
+    ,   .port_clk3("PORT_UNUSED")
+    ,   .port_clk4("PORT_UNUSED")
+    ,   .port_clk5("PORT_UNUSED")
+    ,   .port_clkena0("PORT_UNUSED")
+    ,   .port_clkena1("PORT_UNUSED")
+    ,   .port_clkena2("PORT_UNUSED")
+    ,   .port_clkena3("PORT_UNUSED")
+    ,   .port_clkena4("PORT_UNUSED")
+    ,   .port_clkena5("PORT_UNUSED")
+    ,   .port_extclk0("PORT_UNUSED")
+    ,   .port_extclk1("PORT_UNUSED")
+    ,   .port_extclk2("PORT_UNUSED")
+    ,   .port_extclk3("PORT_UNUSED")
+    ,   .self_reset_on_loss_lock("ON")
+    ,   .width_clock(5)
+    ) pll
+    (   .areset(!reset_n)
+    ,   .inclk(native_clk)
+    ,   .clk(target_clk)
+    ,   .locked(locked)
+    ,   .activeclock()
+    ,   .clkbad()
+    ,   .clkena({6{1'b1}})
+    ,   .clkloss()
+    ,   .clkswitch(1'b0)
+    ,   .configupdate(1'b0)
+    ,   .extclkena({4{1'b1}})
+    ,   .fbin(1'b1)
+    ,   .fbmimicbidir()
+    ,   .fbout()
+    ,   .fref()
+    ,   .icdrclk()
+    ,   .pfdena(1'b1)
+    ,   .phasecounterselect({4{1'b1}})
+    ,   .phasedone()
+    ,   .phasestep(1'b1)
+    ,   .phaseupdown(1'b1)
+    ,   .pllena(1'b1)
+    ,   .scanaclr(1'b0)
+    ,   .scanclk(1'b0)
+    ,   .scanclkena(1'b1)
+    ,   .scandata(1'b0)
+    ,   .scandataout()
+    ,   .scandone()
+    ,   .scanread(1'b0)
+    ,   .scanwrite(1'b0)
+    ,   .sclkout0()
+    ,   .sclkout1()
+    ,   .vcooverrange()
+    ,   .vcounderrange()
+    );
+
+`endif
+
+always_latch begin
+    `ifndef SYNTHESIS
+        target_clk = native_clk;
+        locked = 1;
+    `endif
+
+    if (!reset_n || !locked) state = AWAIT_LOCKED;
+
+    case (state)
+        AWAIT_LOCKED: if (locked) state = AWAIT_LOW;
+        AWAIT_LOW: if (!target_clk) state = AWAIT_HIGH;
+        AWAIT_HIGH: if (target_clk) state = AWAIT_LOW_2;
+        AWAIT_LOW_2: if (!target_clk) state = READY;
+    endcase
+
+    reset = !(state == READY);
+end
+
+endmodule
diff --git a/hdl/top.sv b/hdl/top.sv
index 8d83f35..46620cb 100644
--- a/hdl/top.sv
+++ b/hdl/top.sv
@@ -4,14 +4,22 @@ module top
     #(  ADDR_BITS   = 14
     ,   DATA_BITS   = 12
     )
-    (   input   bit clk     // verilator public
-    ,   input   bit reset_n // verilator public
+    (   input   bit native_clk  // verilator public
+    ,   input   bit reset_n     // verilator public
     );
 
-bit reset = 0;
-bit have_reset = 0;
-always_ff @(posedge clk) if (reset) have_reset <= 1;
-assign reset = !reset_n || !have_reset;
+bit clk;
+bit reset;
+
+clock
+    #(  .DIVIDE_BY(10)
+    ,   .MULTIPLY_BY(9)
+    ) pll
+    (   .native_clk(native_clk)
+    ,   .reset_n(reset_n)
+    ,   .target_clk(clk)
+    ,   .reset(reset)
+    );
 
 bit mem_ready;
 bit mem_valid;
diff --git a/sim/main.cpp b/sim/main.cpp
index 9bf42bd..f082464 100644
--- a/sim/main.cpp
+++ b/sim/main.cpp
@@ -23,16 +23,16 @@ int main(int argc, const char *argv[])
 
     std::uint64_t time = 0;
 
-    top.clk = 0;
+    top.native_clk = 0;
     top.reset_n = 0;
     top.eval();
     vcd.dump(++time);
 
-    top.clk = 1;
+    top.native_clk = 1;
     top.eval();
     vcd.dump(++time);
 
-    top.clk = 0;
+    top.native_clk = 0;
     top.reset_n = 1;
     top.eval();
     vcd.dump(++time);
@@ -40,10 +40,10 @@ int main(int argc, const char *argv[])
     std::cout << "*** MAIN LOOP ***\n";
 
     for (unsigned int i = 0; i < 100000 && !Verilated::gotFinish(); ++i) {
-        top.clk = 1;
+        top.native_clk = 1;
         top.eval();
         vcd.dump(++time);
-        top.clk = 0;
+        top.native_clk = 0;
         top.eval();
         vcd.dump(++time);
     }