1 files changed, 40 insertions, 0 deletions
diff --git a/zpu/hdl/zpu4/test/interrupt/int.c b/zpu/hdl/zpu4/test/interrupt/int.c
new file mode 100644
index 0000000..6ab28f7
--- /dev/null
+++ b/zpu/hdl/zpu4/test/interrupt/int.c
@@ -0,0 +1,40 @@
+/*
+ * Shows usage of interrupts. Goes along with zpu_core_small_wip.vhd.
+ */
+#include <stdio.h>
+
+
+volatile int counter;
+
+/* Example of single, fixed interval non-maskable, nested interrupt. The interrupt signal is
+ * held high for enough cycles to guarantee that it will be noticed, i.e. longer than
+ * any io access + 4 cycles roughly.
+ * 
+ * Any non-trivial interrupt controller would have support for
+ * acknowledging interrupts(i.e. keep interrupts asserted until
+ * software acknowledges them via memory mapped IO).
+ */
+void  _zpu_interrupt(void)
+{
+	/* interrupts are enabled so we need to finish up quickly,
+	 * lest we will get infinite recursion!*/
+	counter++;
+}
+
+int main(int argc, char **argv)
+{
+	int t;
+	t=counter;
+	for (;;)
+	{
+		if (t==counter)
+		{
+			puts("No interrupt\n");
+		} else
+		{
+			puts("Got interrupt\n");
+			t=counter;
+		}
+	}
+    
+}