improved README, default clauses

README.md

@@ -2,7 +2,7 @@
 
 # Small Programmable Interrupt Timer
 
-TinyTapeout is an educational project that aims to make it easier and cheaper than ever to get your digital designs manufactured on a real chip! This is my submission for TinyTapeout 4 in early September 2023.
+TinyTapeout is an educational project that aims to make it easier and cheaper than ever to get your digital designs manufactured on a real chip! This is my submission for TinyTapeout 5 in early November 2023.
 
 A programmable interrupt timer allows you to specify when a digital line is pulled high after a given number of clock ticks, the timer can either repeat or be one-shot.
 
@@ -13,6 +13,9 @@ TODO: how to configure the third register, the low byte of the counter.
 ## Starting the timer.
 Configuring the third register is what starts the timer as the other two registers are optional. The default settings if the first register isn't set are to be a one-shot timer with no clock divider.
 
+## RTL errata
+
+
 
 # Want to see your own digital design taped out to an ASIC?
 Go to https://tinytapeout.com for instructions!

src/test.py

@@ -29,7 +29,7 @@ async def test_no_config(dut):
 
 
 @cocotb.test()
-async def test_one_shot(dut):
+async def test_one_shot_no_divider(dut):
     dut._log.info("start")
     clock = Clock(dut.clk, 10, units="us")
     cocotb.start_soon(clock.start())
@@ -80,16 +80,16 @@ async def repeating_no_divider(dut):
     await ClockCycles(dut.clk, 2)
 
     dut.uio_in.value = 0xA0  # set we high and config_address to 0b10
-    dut.ui_in.value = 0x0A
+    dut.ui_in.value = 0x0A  # counter set to 10
     await ClockCycles(dut.clk, 13)
     dut._log.info("checking that interrupt is high")
-    assert dut.uo_out.value == 0b01001000
+    assert dut.uo_out.value == 0b0100_1000
     assert dut.uio_out.value == 0b0000_0001
 
     dut.uio_in.value = 0x0  # unset we so we no longer configure registers.
     await ClockCycles(dut.clk, 11)
     dut._log.info("checking that interrupt is high")
-    assert dut.uo_out.value == 0b01001000
+    assert dut.uo_out.value == 0b0100_1000
     assert dut.uio_out.value == 0b0000_0001
 
 

src/tt_um_minipit_stevej.v

@@ -73,8 +73,7 @@ module tt_um_minipit_stevej (
                         current_count <= 0;
                         counter_set <= 1;
                     end
-                    2'b11: begin // unused
-                    end
+                    default: begin end
                 endcase
             end // end config logic
 
@@ -85,12 +84,11 @@ module tt_um_minipit_stevej (
                     current_count <= current_count + 1;
                 end
             end else if (counter_set) begin
-                `ifdef FORMAL
-                    assert(!divider_on);
-                `endif
                 current_count <= current_count + 1;
+            end else begin
+                current_count <= current_count;
             end
-            // todo: unset the interrupt
+
             if (counter_set && (current_count == counter)) begin
                 // pull interrupt line high for one clock cycle
                 interrupting <= 1;
@@ -99,7 +97,7 @@ module tt_um_minipit_stevej (
                 end
                 // on a rollover of divider_count, reset the interrupt
                 if (divider_on && (divider_count > 0)) begin
-                    interrupting <= 0; // this is hokey.
+                    interrupting <= 0;
                 end
             end else begin
                 interrupting <= 0;