From 4cbb661f4847cb822009bd4dded3b263c63b83fe Mon Sep 17 00:00:00 2001
From: Andrew Alderwick <andrew@alderwick.co.uk>
Date: Wed, 5 Jan 2022 17:27:01 +0000
Subject: [PATCH] Implement System/vector for debugging.

---
 projects/examples/blank.tal |  4 ++--
 src/devices/system.c        | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/projects/examples/blank.tal b/projects/examples/blank.tal
index d0ae748..050eefe 100644
--- a/projects/examples/blank.tal
+++ b/projects/examples/blank.tal
@@ -22,9 +22,9 @@
 
 ( devices )
 
-|00 @System     &vector $2 &wst      $1 &rst    $1 &pad    $4 &r      $2 &g       $2 &b       $2 &debug  $1 &halt $1
+|00 @System     &vector $2 &wst      $1 &rst    $1 &eaddr  $2 &ecode  $1 &pad     $1 &r       $2 &g      $2 &b     $2 &debug  $1 &halt $1
 |10 @Console    &vector $2 &read     $1 &pad    $5 &write  $1 &error  $1
-|20 @Screen     &vector $2 &width    $2 &height $2 &auto   $1 &pad    $1 &x       $2 &y       $2 &addr   $2 &pixel  $1 &sprite $1
+|20 @Screen     &vector $2 &width    $2 &height $2 &auto   $1 &pad    $1 &x       $2 &y       $2 &addr   $2 &pixel $1 &sprite $1
 |30 @Audio0     &vector $2 &position $2 &output $1 &pad    $3 &adsr   $2 &length  $2 &addr    $2 &volume $1 &pitch $1
 |40 @Audio1     &vector $2 &position $2 &output $1 &pad    $3 &adsr   $2 &length  $2 &addr    $2 &volume $1 &pitch $1
 |50 @Audio2     &vector $2 &position $2 &output $1 &pad    $3 &adsr   $2 &length  $2 &addr    $2 &volume $1 &pitch $1
diff --git a/src/devices/system.c b/src/devices/system.c
index a6eff79..6e38e73 100644
--- a/src/devices/system.c
+++ b/src/devices/system.c
@@ -25,6 +25,16 @@ static const char *errors[] = {
 int
 uxn_halt(Uxn *u, Uint8 error, Uint16 addr)
 {
+	Device *d = &u->dev[0];
+	Uint16 vec = d->vector;
+	if(vec) {
+		d->vector = 0; /* need to rearm to run System/vector again */
+		DEVPOKE16(0x4, addr);
+		d->dat[0x6] = error;
+		if(error != 2) /* working stack overflow has special treatment */
+			vec += 0x0004;
+		return uxn_eval(u, vec);
+	}
 	fprintf(stderr, "Halted: %s#%04x, at 0x%04x\n", errors[error], u->ram[addr], addr);
 	return 0;
 }
@@ -45,6 +55,7 @@ void
 system_deo(Device *d, Uint8 port)
 {
 	switch(port) {
+	case 0x1: DEVPEEK16(d->vector, 0x0); break;
 	case 0x2: d->u->wst.ptr = d->dat[port]; break;
 	case 0x3: d->u->rst.ptr = d->dat[port]; break;
 	default: system_deo_special(d, port);