added IEC support to CHRIN and CHROUT

c64/kernal/chrin.s

@@ -10,15 +10,42 @@
 
 ;; XXX currently does not preserve register Y, to be fixed!
 
-	;;  Reads a byte of input, unless from keyboard.
+	;; Reads a byte of input, unless from keyboard.
 	;; If from keyboard, then it gets a whole line of input, and returns the first char.
 	;; Repeated calls after that read out the successive bytes of the line of input.
+
 chrin:
+	;; First determine the device number
+	lda DFLTN
+
+	beq chrin_keyboard ; #$00 - keyboard
+	;; XXX add screen support
+
+	jsr iec_devnum_check
+	bcs chrin_done_fail ; not a supported device
+
+chrin_iec:
+
+	jsr JACPTR
+	bcs chrin_done_fail
+	;; FALLTROUGH
+
+chrin_done:
+	clc ; indicate success
+	rts
+
+chrin_done_fail:
+	sec ; indicate failure
+	rts
+
+chrin_keyboard:
+
 	;; Save X
 	txa
 	pha
 
-chrin_repeat:	
+chrin_repeat:
+
 	;; Do we have a line of input we are currently returning?
 	;; If so, return the next byte, and clear the flag when we reach the end.
 

c64/kernal/chrout.s

@@ -10,7 +10,6 @@
 
 
 chrout:
-	;; Crude implementation of character output	
 
 	;; Save X and Y values
 	;; (Confirmed by writing a test program that X and Y
@@ -22,7 +21,27 @@ chrout:
 	tya
 	pha
 	php
-	sei
+
+	;; First determine the device number
+	lda DFLTO
+
+	cmp #$03 ; screen
+	beq chrout_screen
+	
+	jsr iec_devnum_check
+	bcs chrout_done_fail ; not a supported device
+
+chrout_iec:
+
+	lda last_printed_character_ascii
+	jsr JCIOUT
+	bcs chrout_done_fail
+	jmp chrout_done
+
+chrout_screen:
+
+	;; Crude implementation of character output	
+	sei ;; XXX why do we need to disable interrupts?
 	
 	jsr hide_cursor_if_visible
 	
@@ -392,7 +411,20 @@ chrout_done:
 	pla
 	tax
 	lda last_printed_character_ascii
-	clc 			; indicate success
+	clc ; indicate success
+	rts
+
+chrout_done_fail:
+	jsr show_cursor_if_enabled
+	
+	plp
+	
+	;; Restore X and Y, set carry to mark success on exit
+	pla
+	tay
+	pla
+	tax
+	sec ; indicate failure
 	rts
 
 screen_grow_logical_line:

c64/kernal/clrchn.s

@@ -8,6 +8,7 @@
 ;; CPU registers that has to be preserved (see [RG64]): .Y
 ;;
 
+
 clrchn:
 
 	;; Handle IEC input device
@@ -24,7 +25,7 @@ clrchn:
 	;; Handle IEC output device
 	jsr unlsn
 *
-clrchn_reset:
+clrchn_reset: ;; entry needed by CHRIN
 	;; Set input device number to keyboard
 	lda #$00
 	sta DFLTN