From 1005ee49524448938a3ca96dbc0d2d6cea273fa1 Mon Sep 17 00:00:00 2001
From: Paul Gardner-Stephen <paul@servalproject.org>
Date: Sun, 5 May 2019 02:02:01 +0930
Subject: [PATCH] fix detection and reporting of FILE NOT FOUND error

---
 c64/basic/cmd_load.s                  |  2 +-
 c64/kernal/iec_rx_byte.s              | 14 ++++++++++----
 c64/kernal/iec_turnaround_to_listen.s | 23 +++++++++++------------
 c64/kernal/load.s                     | 20 +++++++++++++-------
 4 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/c64/basic/cmd_load.s b/c64/basic/cmd_load.s
index 23288871..000743fd 100644
--- a/c64/basic/cmd_load.s
+++ b/c64/basic/cmd_load.s
@@ -64,7 +64,7 @@ got_filename:
 	;; error code to X, decrement, and handle normally
 	tax
 	dex
-	jmp do_LOAD_error
+	jmp do_basic_error
 	
 *
 	;; $YYXX is the last loaded address, so store it
diff --git a/c64/kernal/iec_rx_byte.s b/c64/kernal/iec_rx_byte.s
index 9d168597..9c7f6768 100644
--- a/c64/kernal/iec_rx_byte.s
+++ b/c64/kernal/iec_rx_byte.s
@@ -23,27 +23,33 @@ iec_rx_clk_wait:
 	rol
 	bpl not_eoi
 	dex
+	cpx #$21
+	bne not_rx_timeout
+	;; Time out waiting for CLK to assert again.
+	;;  = error
+	sec
+	rts
+not_rx_timeout:
+	cpx #$00
 	bpl iec_rx_clk_wait
 
 	;; Remember EOI condition
 	lda IOSTATUS
 	ora #$40
 	sta IOSTATUS
-	
+
 	;; EOI timeout: So pulse DATA line for 60 usec
 	jsr iec_assert_data
 	jsr iec_wait60us
 	jsr iec_release_clk_and_data
 
-	;; Assert some kind of flag so that we know if it was EOI = the last byte on offer
-	
 	;; And still wait for CLK to be asserted
 	;; XXX - This will cause periodic EOI pulses if the sender takes too long.
 	;; That is probably ok.
 	ldx #$7f
 	jmp iec_rx_clk_wait
 
-not_eoi:	
+not_eoi:
 	;; CLK is now low.  Latch input bits in on rising edge
 	;; of CLK, eight times for eight bits.
 	ldx #7
diff --git a/c64/kernal/iec_turnaround_to_listen.s b/c64/kernal/iec_turnaround_to_listen.s
index db021689..25220abf 100644
--- a/c64/kernal/iec_turnaround_to_listen.s
+++ b/c64/kernal/iec_turnaround_to_listen.s
@@ -18,23 +18,22 @@ iec_turnaround_to_listen:
 	;; page 8 tells us we should not do anything here after waiting for
 	;; the clock line to assert.
 	
-;; 	ldx #$ff
-;; *	lda $dd00
-;; 	and #$40
-;; 	bne +
-;; 	dex
-;; 	bne -
+ 	ldx #$ff
+ *	lda $dd00
+ 	and #$40
+ 	bne +
+ 	dex
+ 	bne -
 
-	;; jsr printf
-	;; .byte "TURNAROUND FAILED - FILE NOT FOUND?",$0d,$00
+	 jsr printf
+	 .byte "TURNAROUND FAILED - FILE NOT FOUND?",$0d,$00
 	
 	;; ;; Timeout = file not found error
 	;; ;; (https://www.pagetable.com/?p=1023)
-	;; lda #4
-	;; sec
-	;; rts
+	 lda #4
+	 sec
+	 rts
 *
-
 	;; ATN turn around successful
 	clc
 	rts
diff --git a/c64/kernal/load.s b/c64/kernal/load.s
index 699781bb..059245e4 100644
--- a/c64/kernal/load.s
+++ b/c64/kernal/load.s
@@ -126,24 +126,23 @@ sent_filename:
 	jsr iec_turnaround_to_listen
 	bcs load_error
 
-	jsr printf
-	.byte "LOADING",$0d,0
-
-	
 	;; Get load address and store it if secondary address is zero
 	jsr iec_rx_byte
-	bcs load_error
+	bcs file_not_found_error
 	ldx current_secondary_address
 	beq +
 	sta load_save_start_ptr+0
 *
 	jsr iec_rx_byte
-	bcs load_error
+	bcs file_not_found_error
 	ldx current_secondary_address
 	beq +
 	sta load_save_start_ptr+1
 *
 
+	jsr printf
+	.byte "LOADING",$0d,0
+		
 load_loop:
 	;; We are now ready to receive bytes
 	jsr iec_rx_byte
@@ -206,10 +205,17 @@ load_error:
 
 	;; XXX - Indicate KERNAL (not BASIC) LOAD error condtion
 	sec
-	lda #$02
+	lda #28
 	
 	;; Re-enable interrupts and return
 	cli
 	;; (iec_tx_byte will have set/cleared C flag and put result code
 	;; in A if it was an error).
 	rts
+
+file_not_found_error:
+	;; Indicate KERNAL error condition for file not found
+	sec
+	lda #$04
+	cli
+	rts