From a80d49059019a15889101860f95fcae301da05e4 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Fri, 26 Jul 2019 18:30:07 +0200
Subject: [PATCH] fixes to Kernal character handling routines

---
 c64/basic/wedge_dos.s |  1 +
 c64/kernal/chkinout.s | 14 +++++++-------
 c64/kernal/chrin.s    |  6 ++++--
 c64/kernal/chrout.s   | 43 +++++++++++++++++++++++++++++--------------
 c64/kernal/clall.s    |  6 +++++-
 5 files changed, 46 insertions(+), 24 deletions(-)

diff --git a/c64/basic/wedge_dos.s b/c64/basic/wedge_dos.s
index 041949c7..5408f8bb 100644
--- a/c64/basic/wedge_dos.s
+++ b/c64/basic/wedge_dos.s
@@ -103,6 +103,7 @@ wedge_dos_status:
 	;; Print out everything retrieved from the drive
 	bne +
 	jsr via_IBASIN
+	bcs wedge_dos_basic_error
 	jsr via_IBSOUT
 	jmp -
 *
diff --git a/c64/kernal/chkinout.s b/c64/kernal/chkinout.s
index 1af2fc02..1075665c 100644
--- a/c64/kernal/chkinout.s
+++ b/c64/kernal/chkinout.s
@@ -44,13 +44,13 @@ chkin:
 	lda FAT,Y
 	jsr iec_check_devnum
 	bcs chkin_set_device
-
+	
 	jsr talk
-	bcs chkinout_end ; don't set DFLTN in case of failure
+	bcs chkinout_device_not_present ; don't set DFLTN in case of failure
 
 	lda LAT, Y
 	jsr tksa
-	bcs chkinout_end
+	bcs chkinout_device_not_present
 
 chkin_set_device:
 	lda FAT,Y
@@ -126,16 +126,16 @@ ckout:
 	;; For IEC devices, send LISTEN + SECOND first
 	lda FAT,Y
 	jsr iec_check_devnum
-	bcs chkin_set_device
+	bcs chkout_set_device
 
 	jsr listen
-	bcs chkinout_end ; don't set DFLTO in case of failure
+	bcs chkinout_device_not_present ; don't set DFLTO in case of failure
 
 	lda LAT, Y
 	jsr second
-	bcs chkinout_end
+	bcs chkinout_device_not_present
 
-hkout_set_device:
+chkout_set_device:
 	lda FAT,Y
 	sta DFLTO
 	clc ; for success
diff --git a/c64/kernal/chrin.s b/c64/kernal/chrin.s
index b20014e2..8a84f5d6 100644
--- a/c64/kernal/chrin.s
+++ b/c64/kernal/chrin.s
@@ -15,14 +15,16 @@
 ;; Repeated calls after that read out the successive bytes of the line of input.
 
 chrin:
-	;; First determine the device number
+
+	;; Determine the device number
 	lda DFLTN
 
 	beq chrin_keyboard ; #$00 - keyboard
 	;; XXX add screen support
 
 	jsr iec_check_devnum
-	bcs chrin_done_fail ; not a supported device
+	bcc chrin_iec
+	jmp lvs_device_not_found_error ;  not a supported device
 
 chrin_iec:
 
diff --git a/c64/kernal/chrout.s b/c64/kernal/chrout.s
index 48f5a606..6f340a0f 100644
--- a/c64/kernal/chrout.s
+++ b/c64/kernal/chrout.s
@@ -11,40 +11,41 @@
 
 chrout:
 
+	sta last_printed_character_ascii
+
 	;; Save X and Y values
 	;; (Confirmed by writing a test program that X and Y
 	;; don't get modified, in agreement with C64 PRG's
 	;; description of CHROUT)
-	sta last_printed_character_ascii
 	txa
 	pha
 	tya
 	pha
 	php
 
-	;; First determine the device number
+	;; Determine the device number
 	lda DFLTO
 
 	cmp #$03 ; screen
 	beq chrout_screen
 
 	jsr iec_check_devnum
-	bcs chrout_done_fail ; not a supported device
+	bcs chrout_done_unknown_device ; not a supported device
 
 chrout_iec:
 
 	lda last_printed_character_ascii
 	jsr JCIOUT
 	bcc chrout_done
-	
+
 	;; FALLTROUGH
 
 chrout_done_fail:
 	jsr show_cursor_if_enabled
-	
+
 	plp
-	
-	;; Restore X and Y, set carry to mark success on exit
+
+	;; Restore X and Y
 	pla
 	tay
 	pla
@@ -52,12 +53,26 @@ chrout_done_fail:
 	sec ; indicate failure
 	rts
 
+chrout_done_unknown_device:
+	jsr show_cursor_if_enabled
+
+	plp
+
+	;; Restore X and Y
+	pla
+	tay
+	pla
+	tax
+
+	;; End wioth error
+	jmp lvs_device_not_found_error
+
 chrout_done:
 	jsr show_cursor_if_enabled
-	
+
 	plp
-	
-	;; Restore X and Y, set carry to mark success on exit
+
+	;; Restore X and Y
 	pla
 	tay
 	pla
@@ -70,12 +85,12 @@ chrout_screen:
 
 	;; Crude implementation of character output	
 	sei ;; XXX why do we need to disable interrupts?
-	
+
 	jsr hide_cursor_if_visible
-	
+
 	lda last_printed_character_ascii
 	tax
-	
+
 	;; Check for special characters
 
 	cmp #$00
@@ -89,7 +104,7 @@ not_00:
 	bne not_0a
 	jmp chrout_done
 not_0a:
-	
+
 	;; Carriage return
 	cmp #$0d
 	bne not_0d
diff --git a/c64/kernal/clall.s b/c64/kernal/clall.s
index 01145a00..ba595c20 100644
--- a/c64/kernal/clall.s
+++ b/c64/kernal/clall.s
@@ -31,4 +31,8 @@ clall:
 	tay
 
 	;; 'C64 Programmers Reference Guide', page 281, claims it calls CLRCHN too
-	jmp clrchn
+	jsr clrchn
+	
+	;; Not sure whether original Kernal does so, but it seems sane to also clear possible errors
+	jmp kernalstatus_reset
+