From 180c88ef42646b8a60d39c1a15beb407abdd1777 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Sun, 1 Sep 2019 16:20:36 +0200
Subject: [PATCH] reenabled BRK handler, now prints BRK address

---
 STATUS.md                                     |  3 ++-
 c64/aliases/,aliases_ram_lowmem.s             |  6 +-----
 c64/basic/basic_warm_start.s                  | 20 +++++++++++++++++--
 .../interrupts/fe47.default_nmi_handler.s     |  6 +++++-
 c64/kernal/interrupts/irq_handler.s           | 19 ++++++++++++------
 src/compress_text.c                           |  2 +-
 6 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/STATUS.md b/STATUS.md
index 4e9cf6bd..65bf9f8f 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -7,6 +7,7 @@ Here are the features of the Open ROMs not found in the original ROMs from the 8
 * joystick (port 1) can be used to move text cursor
 * uses RAM under ROM and I/O: 61436 bytes free
 * cold/warm start silences multiple SID chips - all $D4xx and $D5xx addresses
+* wark start due to BRK prints out the instruction address
 * extended `LOAD` command
     * start/end addresses are displayed, in the Final cartridge style
     * command with just the file name tries to use the last device if it's number seems sane; otherwise uses 8
@@ -28,7 +29,7 @@ The following ROM features are currently missing:
 * tape support
 * RS-232 support
 * breaking Kernal routines with RUN/STOP key
-* BRK handling; NMI/IRQ handling is incomplete
+* NMI andling is incomplete
 
 
 # API status
diff --git a/c64/aliases/,aliases_ram_lowmem.s b/c64/aliases/,aliases_ram_lowmem.s
index 6108e28e..d72deec7 100644
--- a/c64/aliases/,aliases_ram_lowmem.s
+++ b/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
 
diff --git a/c64/basic/basic_warm_start.s b/c64/basic/basic_warm_start.s
index e8e51b31..adeb329e 100644
--- a/c64/basic/basic_warm_start.s
+++ b/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
-	
+
diff --git a/c64/kernal/interrupts/fe47.default_nmi_handler.s b/c64/kernal/interrupts/fe47.default_nmi_handler.s
index 8814ac2c..1a1c915f 100644
--- a/c64/kernal/interrupts/fe47.default_nmi_handler.s
+++ b/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)
 
diff --git a/c64/kernal/interrupts/irq_handler.s b/c64/kernal/interrupts/irq_handler.s
index 99733333..292f88e0 100644
--- a/c64/kernal/interrupts/irq_handler.s
+++ b/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)
 
diff --git a/src/compress_text.c b/src/compress_text.c
index 57c02f19..576d4d09 100644
--- a/src/compress_text.c
+++ b/src/compress_text.c
@@ -161,7 +161,7 @@ char *error_list[]={
   "READY.\r", // #29       // https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zconcepts/zconc_whatistsonative.htm https://github.com/stefanhaustein/expressionparser
   "NTSC, ", // #30
   "PAL, ", // #31
-  "", // unused for now
+  "BRK AT $", // #32
   "ERROR", // #33            // Simply the word error that is attached to the other parts of messages https://fjkraan.home.xs4all.nl/comp/apple2faq/app2asoftfaq.html
   "BYTES FREE\r\r", // #34 // https://github.com/stefanhaustein/expressionparser
   "MEMORY CORRUPT", // #35