X-Git-Url: https://hackdaworld.org/gitweb/?p=my-code%2Farm.git;a=blobdiff_plain;f=betty%2Fstartup.s;fp=betty%2Fstartup.s;h=d393d32a35e0763ebc95a8b32f0401811829fcc7;hp=fb42ac7deecf00f97af2e2bf7053221bb53675b6;hb=916c8dd1dfa2414ae8b58ab1e3d477b24c553815;hpb=6292cc9190f6e7f36a3634057740e770d58d7460

diff --git a/betty/startup.s b/betty/startup.s
index fb42ac7..d393d32 100644
--- a/betty/startup.s
+++ b/betty/startup.s
@@ -49,6 +49,13 @@
 .arm
 
 	# exception handling must go to the very beginning
+	#
+	# concerning irq:
+	#  - the ldr is at 0x18
+	#  - pc will be 0x18 + 8 at the moment of ldr (pipeline)
+	#  - substract 0xff0 => 0xfffff030
+	#  - that's the vectored address register
+	#  - the vic put in there the address of our service routine
 
 	ldr pc, handler_reset
 	ldr pc, handler_undef_instruction
@@ -56,7 +63,7 @@
 	ldr pc, handler_prefetch_abort
 	ldr pc, handler_data_abort
 	nop
-	ldr pc, handler_irq
+	ldr pc, [pc, #-0xff0]
 	ldr pc, handler_fiq
 
 handler_reset: .word handle_reset
@@ -64,7 +71,6 @@ handler_undef_instruction: .word interrupt_handler_undef_instruction
 handler_soft_ir: .word interrupt_handler_soft_ir
 handler_prefetch_abort: .word interrupt_handler_prefetch_abort
 handler_data_abort: .word interrupt_handler_data_abort
-handler_irq: .word interrupt_handler_irq
 handler_fiq: .word interrupt_handler_fiq
 
 	# reset handling goes here