From a3c405ddb416bbf6848c31aff73803bf45aa0cee Mon Sep 17 00:00:00 2001
From: Tam Do <tdo.pro@gmail.com>
Date: Tue, 17 Jul 2018 19:27:44 -0500
Subject: [PATCH] allow polling interrupt flag within ISR

---
 simavr/sim/sim_interrupts.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/simavr/sim/sim_interrupts.c b/simavr/sim/sim_interrupts.c
index b689a94..68c3bff 100644
--- a/simavr/sim/sim_interrupts.c
+++ b/simavr/sim/sim_interrupts.c
@@ -114,13 +114,15 @@ avr_raise_interrupt(
 {
 	if (!vector || !vector->vector)
 		return 0;
+
 	if (vector->pending) {
 		if (vector->trace)
 			printf("IRQ%d:I=%d already raised (enabled %d) (cycle %lld pc 0x%x)\n",
 				vector->vector, !!avr->sreg[S_I], avr_regbit_get(avr, vector->enable),
 				(long long int)avr->cycle, avr->pc);
-		return 0;
+        // no return - polling ISR within interrupt allowed
 	}
+
 	if (vector->trace)
 		printf("IRQ%d raising (enabled %d)\n",
 			vector->vector, avr_regbit_get(avr, vector->enable));
-- 
2.39.5