1 files changed, 78 insertions, 0 deletions
diff --git a/ports/risc-v64/gnu/example_build/erbium/trap.c b/ports/risc-v64/gnu/example_build/erbium/trap.c
new file mode 100644
index 00000000..d839e6ea
--- /dev/null
+++ b/ports/risc-v64/gnu/example_build/erbium/trap.c
@@ -0,0 +1,78 @@
+/***************************************************************************
+ * Copyright (c) 2026 Eclipse ThreadX contributors
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the MIT License which is available at
+ * https://opensource.org/licenses/MIT.
+ *
+ * AI Disclosure: This file was largely AI-generated by Claude Code (Opus 5.5).
+ * The AI-generated portions may be considered public domain (CC0-1.0)
+ * and not subject to the project's licence. The human contributor has
+ * reviewed and verified that the code is correct.
+ *
+ * SPDX-License-Identifier: MIT and CC0-1.0
+ **************************************************************************/
+
+/* Machine-mode trap dispatcher for the Erbium example.  */
+
+#include "csr.h"
+#include "uart.h"
+#include "hwtimer.h"
+#include "plic.h"
+#include <stdint.h>
+#include <tx_api.h>
+
+#define MCAUSE_INT_BIT          ((uintptr_t)1 << (__riscv_xlen - 1))
+#define MCAUSE_M_TIMER          (MCAUSE_INT_BIT | 7u)
+#define MCAUSE_M_EXTERNAL       (MCAUSE_INT_BIT | 11u)
+
+extern void _tx_timer_interrupt(void);
+
+static void print_hex(uintptr_t val)
+{
+    const char digits[] = "0123456789ABCDEF";
+
+    uart_putc('0');
+    uart_putc('x');
+    for (int i = (int)(sizeof(uintptr_t) * 2) - 1; i >= 0; i--)
+        uart_putc(digits[(val >> (i * 4)) & 0xFu]);
+    uart_putc('\r');
+    uart_putc('\n');
+}
+
+static void trap_halt(const char *reason, uintptr_t mcause, uintptr_t mepc, uintptr_t mtval)
+{
+    uart_puts(reason);
+    uart_puts("mcause:");
+    print_hex(mcause);
+    uart_puts("mepc:");
+    print_hex(mepc);
+    uart_puts("mtval:");
+    print_hex(mtval);
+
+    /* Spin rather than WFI, as everywhere else in this example.  */
+    while (1)
+        ;
+}
+
+void trap_handler(uintptr_t mcause, uintptr_t mepc, uintptr_t mtval)
+{
+    if (mcause == MCAUSE_M_TIMER)
+    {
+        hwtimer_handler();
+        _tx_timer_interrupt();
+    }
+    else if (mcause == MCAUSE_M_EXTERNAL)
+    {
+        if (plic_irq_intr() != 0)
+            trap_halt("[INTERRUPT]: external interrupt not handled, halting", mcause, mepc, mtval);
+    }
+    else if ((mcause & MCAUSE_INT_BIT) != 0u)
+    {
+        trap_halt("[INTERRUPT]: unexpected interrupt, halting", mcause, mepc, mtval);
+    }
+    else
+    {
+        trap_halt("[EXCEPTION]: unhandled exception, halting", mcause, mepc, mtval);
+    }
+}