From 6bf715e610a32a517d80851a805102764e19c0e0 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Wed, 17 Jul 2019 21:56:42 +0200
Subject: [PATCH] IEC routines can now be called with enabled IRQs

---
 c64/kernal/iec_rx_byte.s   |  6 ++++++
 c64/kernal/iec_tx_common.s |  5 +++++
 c64/kernal/load.s          | 12 +++---------
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/c64/kernal/iec_rx_byte.s b/c64/kernal/iec_rx_byte.s
index d91a857d..4a7eb996 100644
--- a/c64/kernal/iec_rx_byte.s
+++ b/c64/kernal/iec_rx_byte.s
@@ -4,6 +4,10 @@
 
 iec_rx_byte:
 
+	;; Timing is critical here - execute on disabled IRQs
+	php
+	sei
+
 	;; First, we wait for the talker to release the CLK line
 	jsr iec_wait_for_clk_release
 
@@ -95,6 +99,7 @@ iec_rx_clk_wait2:
     ;; Timeout
     jsr kernalstatus_EOI
     pla
+    plp
     sec ; XXX confirm that sec is really a way to report timeout here
     rts
 *
@@ -112,6 +117,7 @@ iec_rx_clk_wait2:
 	pla
 
 	;; Return no-error
+	plp
 	clc
 	rts
 
diff --git a/c64/kernal/iec_tx_common.s b/c64/kernal/iec_tx_common.s
index 8de7c891..ef9a5097 100644
--- a/c64/kernal/iec_tx_common.s
+++ b/c64/kernal/iec_tx_common.s
@@ -5,6 +5,10 @@
 
 iec_tx_common:
 
+	;; Timing is critical here - execute on disabled IRQs
+	php
+	sei
+
 	;; Store the byte to send on a stack
 	pha
 
@@ -64,6 +68,7 @@ iec_tx_common_bit_is_sent:
 	bpl iec_tx_common_nextbit
 	pla
 	
+	plp
 	rts ; Flow continues differently for data/command
 	
 iec_tx_common_nextbit:
diff --git a/c64/kernal/load.s b/c64/kernal/load.s
index d9097d95..e075180d 100644
--- a/c64/kernal/load.s
+++ b/c64/kernal/load.s
@@ -33,9 +33,6 @@ load:
 
 	;; We need our helpers to get to filenames under ROMs or IO area
 	jsr install_ram_routines
-	
-	;; Disable IRQs, since timing matters!
-	sei
 
 	;; Display SEARCHING FOR + filename
 	lda MSGFLG
@@ -162,12 +159,15 @@ load_loop:
 	;; to do the memory access
 
 	;; Save byte under ROMs and IO if required
+	php
+	sei
 	ldx #$33
 	stx $01
 	ldy #0
 	sta (load_save_start_ptr),y
 	ldx #$37
 	stx $01
+	plp
 
 	;; Advance pointer
 	inc load_save_start_ptr
@@ -221,34 +221,28 @@ load_done:
 	ldy load_save_start_ptr+1
 
 	clc
-	cli
 	rts
 
 load_wrap_around_error:
 
 	;; This error is probably not even detected by C64 Kernal;
 	;; report BASIC error code that looks the most sane
-	cli
 	lda #B_ERR_OVERFLOW
 	sec
 	rts
-	rts
 
 load_device_not_found_error:
 
-	cli
 	jsr kernalstatus_DEVICE_NOT_FOUND
 	jmp kernalerror_DEVICE_NOT_FOUND
 
 load_file_not_found_error:
 
-	cli
 	jmp kernalerror_FILE_NOT_FOUND
 
 load_error:
 
 	;; XXX should we really return BASIC error code here?
-	cli
 	lda kernal_load_or_verify_flag
 	beq load_verify_error
 	lda #B_ERR_LOAD