reenabled BRK handler, now prints BRK address

c64/aliases/,aliases_ram_lowmem.s

@@ -34,11 +34,7 @@
 	.alias IEC_TMP1   $A3 ; temporary variable for tape and IEC
 	.alias IEC_TMP2   $A4 ; temporary variable for tape and IEC
 
-	;; 2-byte location below seems to be a good place for temporary storage,
-	;; it seems used for timing during tape reads only - see:
-	;; - 'C64 Programmer's Reference Guide', page 314
-	;; - 'Compute's Mapping the Commodore 64', page 32
-	.alias CMP0       $B0 ; $B0-$B1
+	.alias CMP0       $B0 ; $B0-$B1, temporary tape storage, we use it too for BRK instruction address
 	
 	.alias FNLEN      $B7 ; current file name length
 

c64/basic/basic_warm_start.s

@@ -2,6 +2,22 @@
 
 basic_warm_start:
 	jsr install_ram_routines
-	
+
+	;; If warm start caused by BRK, print it address
+	lda CMP0
+	ora CMP0+1
+	beq +
+
+	ldx #32
+	jsr print_packed_message
+
+	lda CMP0+1
+	jsr printf_printhexbyte
+	lda CMP0+0
+	jsr printf_printhexbyte
+	lda #$0D
+	jsr JCHROUT
+
+*
 	jmp basic_main_loop
-	
+

c64/kernal/interrupts/fe47.default_nmi_handler.s

@@ -26,5 +26,9 @@ default_nmi_handler:
 	bcs +
 	jmp return_from_interrupt ; no STOP pressed
 *
-	jmp (CBINV) ; STOP + RESTORE
+	;; STOP + RESTORE - clean the address of the BRK instruction (it's not BRK) first
+	lda #$00
+	sta CMP0+0
+	sta CMP0+1
+	jmp (CBINV)
 

c64/kernal/interrupts/irq_handler.s

@@ -16,12 +16,10 @@ irq_handler:
 	pha
 
 	;; Check if caused by BRK
-
-	;; XXX disabled for now - resets Duotris game, unknown why
-	; tsx
-	; lda $0104, x ; get the pre-interrupt processor state
-	; and #$10
-	; bne irq_handler_brk
+	tsx
+	lda $0104, x ; get the pre-interrupt processor state
+	and #$10
+	bne irq_handler_brk
 
 	;; Not caused by BRK - call interrupt routine (only if initialised)
 	lda CINV
@@ -34,6 +32,15 @@ irq_handler:
 
 irq_handler_brk:
 
+	;; Store BRK adddress, to be displayed
+	sec
+	lda $0105, x
+	sbc #$02
+	sta CMP0+0
+	lda $0106, x
+	sbc #$00
+	sta CMP0+1
+
 	;; Interrupt caused by BRK
 	jmp (CBINV)