From d124349e5036d6fabb21ad89444c7e1aa481f8f6 Mon Sep 17 00:00:00 2001
From: Paul Gardner-Stephen <paul@servalproject.org>
Date: Sat, 4 May 2019 23:05:23 +0930
Subject: [PATCH] handle EOI and generally get closer to a working LOAD routine

---
 c64/kernal/iec_rx_byte.s |  6 ++-
 c64/kernal/load.s        | 94 ++++++----------------------------------
 2 files changed, 18 insertions(+), 82 deletions(-)

diff --git a/c64/kernal/iec_rx_byte.s b/c64/kernal/iec_rx_byte.s
index 78dc715b..599e254d 100644
--- a/c64/kernal/iec_rx_byte.s
+++ b/c64/kernal/iec_rx_byte.s
@@ -31,8 +31,10 @@ iec_rx_clk_wait:
 	dex
 	bpl iec_rx_clk_wait
 
-	inc $0632
-	inc $d020
+	;; Remember EOI condition
+	lda IOSTATUS
+	ora #$40
+	sta IOSTATUS
 	
 	;; EOI timeout: So pulse DATA line for 60 usec
 	jsr iec_assert_data
diff --git a/c64/kernal/load.s b/c64/kernal/load.s
index 66b21f2c..fcdc8d7f 100644
--- a/c64/kernal/load.s
+++ b/c64/kernal/load.s
@@ -15,66 +15,6 @@ load:
 	;; also p16 tells us this routine doesn't mess with the file table in the C64,
 	;; only in the drive.
 	
-	;; Now command device to listen (p16)
-	jsr iec_assert_atn
-	lda #$28
-	jsr iec_tx_byte
-	bcs load_error
-
-	inc $0609
-	
-	lda #$6f ; open channel / data (p3) , required according to p13
-	jsr iec_tx_byte
-	bcs load_error
-	jsr iec_release_atn
-
-
-	;; Send invalid "Q" command to drive as test
-	lda #$51
-	jsr iec_tx_byte
-	bcs load_error
-	lda #$0d
-	jsr iec_tx_byte
-	bcs load_error
-	
-	inc $060a
-
-	;; Now command device to talk (p16)
-	jsr iec_assert_atn
-	lda #$48
-	jsr iec_tx_byte
-	bcs load_error
-
-	lda #$6f ; open channel / data (p3) , required according to p13
-	jsr iec_tx_byte
-	bcs load_error
-	jsr iec_release_atn
-	
-	;; We are currently talker, so do the IEC turn around so that we
-	;; are the listener (p16)
-	jsr iec_turnaround_to_listen
-	bcs load_error
-
-	inc $060b
-
-	jsr printf
-	.byte "READING DATA...",$0d,0
-
-read_loop:	
-*	jsr iec_rx_byte
-	php
-	;;  Write read data to screen for now
-	inc $ff
-	ldx $ff
-	sta $1000,x
-	plp
-	bcs load_done	
-	bcc -
-	jmp read_loop
-	
-
-
-	
 	;; Begin sending under attention
 	jsr iec_assert_atn
 
@@ -108,32 +48,25 @@ read_loop:
 	bcs load_error
 	jsr iec_release_atn
 
-	inc $0608
-	
 	;; Now command device to talk (p16)
 	jsr iec_assert_atn
 	lda #$48
 	jsr iec_tx_byte
 	bcs load_error
 
-	inc $0609
-	
 	lda #$60 ; open channel / data (p3) , required according to p13
 	jsr iec_tx_byte
 	bcs load_error
 	jsr iec_release_atn
 
-	inc $060a
-	
 	;; We are currently talker, so do the IEC turn around so that we
 	;; are the listener (p16)
+	;; An error here means FILE NOT FOUND ?
 	jsr iec_turnaround_to_listen
 	bcs load_error
 
-	inc $060b
-
 	jsr printf
-	.byte "READING DATA...",$0d,0
+	.byte "LOADING",$0d,0
 	
 	;; We are now ready to receive bytes
 *	jsr iec_rx_byte
@@ -143,14 +76,18 @@ read_loop:
 	ldx $ff
 	sta $0400,x
 	plp
-	bcs load_done	
-	bcc -
+	bcs load_error
+
+	;; Check for EOI -- if so, read one last byte
+	lda IOSTATUS
+	and #$40
+	beq -
 
 load_done:
-	;; Close file on drive
+	jsr printf
+	.byte "LOADED",$0d,0
 
-	inc $060c
-	
+	;; Close file on drive
 
 	;; Command drive to listen and to close the file
 	jsr iec_assert_atn
@@ -160,22 +97,19 @@ load_done:
 	jsr iec_tx_byte
 	jsr iec_release_atn
 
-	inc $060d
-	
 	;; Tell drive to unlisten
 	jsr iec_assert_atn
 	lda #$3f
 	jsr iec_tx_byte
 	jsr iec_release_atn
 
-	inc $060e
-	
 	;;  FALL THROUGH
+	clc
 	
 load_error:
 
-	inc $060f
-	
+	;; XXX - Indicate KERNAL (not BASIC) LOAD error condtion
+
 	;; Re-enable interrupts and return
 	cli
 	;; (iec_tx_byte will have set/cleared C flag and put result code