minor comment/documentation cleanups

tridoracpu/tridoracpu.srcs/stackcpu.v

@@ -399,7 +399,10 @@ module stackcpu #(parameter ADDR_WIDTH = 32, WIDTH = 32,
     // process irq
     always @(posedge clk)
     begin
-        if(seq_state == MEM && irq_pending && !(ins_xfer & xfer_r2p))   // in FETCH state, clear irq_pending.
+        // in MEM state, clear irq_pending, when nPC has been set to IV
+        // RET instruction is a special case because we need to use
+        // the new PC that is in mem_data
+        if(seq_state == MEM && irq_pending && !(ins_xfer && xfer_r2p))
             irq_pending <= 0;
         else
             irq_pending <= irq_pending || irq;  // else set irq_pending when irq is high

tridoracpu/tridoracpu.srcs/top.v

@@ -278,6 +278,9 @@ module top(
                         (io_slot == 4) ? tdraudio_rd_data:
     `endif
                         -1;
+    irqctrl irqctrl0(`clock, irq_in, irqc_cs, mem_write_enable,
+            irqc_seten, irqc_rd_data0,
+            irq);
 
      // CPU -----------------------------------------------------------------
     stackcpu cpu0(.clk(`clock), .rst(rst), .irq(irq),
@@ -288,10 +291,6 @@ module top(
         .mem_wait(mem_wait),
         .debug1(led1), .debug2(led2), .debug3(led3));
 
-    // Interrupt Controller
-    irqctrl irqctrl0(`clock, irq_in, irqc_cs, mem_write_enable,
-            irqc_seten, irqc_rd_data0,
-            irq);
 
     // count clock ticks
     // generate interrupt every 20nth of a second