From 44db729d5cbf7578cb0d2d7bdc7d4651886d9f13 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Tue, 23 Jul 2019 20:56:28 +0200
Subject: [PATCH] fixed incorrect byte comparing

---
 c64/basic/select_device.s         | 11 +++++++----
 c64/kernal/iec/iec_devnum_check.s | 12 +++++-------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/c64/basic/select_device.s b/c64/basic/select_device.s
index 48061f8a..f5939033 100644
--- a/c64/basic/select_device.s
+++ b/c64/basic/select_device.s
@@ -1,15 +1,18 @@
 
 select_device:
 
-	;; Take last device number, make sure it's a drive
-	;; If not, set to 8 (first drive number)
+	;; Take last device number, make sure it's a drive - 8 or above. Above 30,
+	;; although illegal for IEC we also consider a drive, as they exists
+	;; drivers assigning these numbers to CBM-DOS capable devices - like some
+	;; IEEE-488 carts.
+	;;
+	;; If current device is not a drive, set device to 8 (first drive number)
 	;; Device number is left in X, for SETFLS Kernal routine
 
 	;; Note: if tape support is introduced here, make sure DOS wedge won't get broken
 
 	ldx current_device_number
-	cpx #$07
-	bpl +
+	cpx #$08
 	bcs +
 	ldx #$08
 *
diff --git a/c64/kernal/iec/iec_devnum_check.s b/c64/kernal/iec/iec_devnum_check.s
index 8fffb64e..84cd506b 100644
--- a/c64/kernal/iec/iec_devnum_check.s
+++ b/c64/kernal/iec/iec_devnum_check.s
@@ -7,18 +7,16 @@
 
 iec_devnum_check:
 	;; 0, 1, 2, or 3 are illegal - reserved for non-IEC devices on Commodore
-	cmp #$03
-	bpl +
+	cmp #$04
 	bcs +
 	;; FALLTROUGH
 iec_devnum_check_failed:
-	sec
+	sec ; indicate non-IEC device
 	rts
 *
-	;; 30 and above are illegal too, due to IEC command encoding scheme,
+	;; 31 and above are illegal too, due to IEC command encoding scheme,
 	;; see https://www.pagetable.com/?p=1031
-	cmp #$1E
-	bpl iec_devnum_check_failed
+	cmp #$1F
 	bcs iec_devnum_check_failed
-	clc
+	;; Carry is clear here - indicates IEC device
 	rts