From cdb5c1eef67830220285fd5893293c54c19224de Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 3 Sep 2020 19:42:10 +0200
Subject: [PATCH] autoswitch to legacy mode if loading file below $0800

---
 src/kernal/board_m65/mega65_imports.s         |  1 +
 src/kernal/board_m65/mega65_load_autoswitch.s | 44 +++++++++++++++++++
 src/kernal/board_m65/mega65_proxies.s         |  6 +++
 src/kernal/iec/load_iec.s                     |  9 ++++
 src/kernal/tape/tape_common.s                 |  8 ++++
 5 files changed, 68 insertions(+)
 create mode 100644 src/kernal/board_m65/mega65_load_autoswitch.s

diff --git a/src/kernal/board_m65/mega65_imports.s b/src/kernal/board_m65/mega65_imports.s
index 68b57db9..b1d5f35b 100644
--- a/src/kernal/board_m65/mega65_imports.s
+++ b/src/kernal/board_m65/mega65_imports.s
@@ -69,6 +69,7 @@
 .label lvs_return_last_address         = KERNAL_0.proxy_K1_lvs_return_last_address
 .label lvs_device_not_found_error      = KERNAL_0.proxy_K1_lvs_device_not_found_error
 .label lvs_load_verify_error           = KERNAL_0.proxy_K1_lvs_load_verify_error
+.label m65_load_autoswitch_tape        = KERNAL_0.proxy_K1_m65_load_autoswitch_tape
 
 .label lvs_check_EAL                   = KERNAL_0.lvs_check_EAL
 .label lvs_STAL_to_MEMUSS              = KERNAL_0.lvs_STAL_to_MEMUSS
diff --git a/src/kernal/board_m65/mega65_load_autoswitch.s b/src/kernal/board_m65/mega65_load_autoswitch.s
new file mode 100644
index 00000000..650dd136
--- /dev/null
+++ b/src/kernal/board_m65/mega65_load_autoswitch.s
@@ -0,0 +1,44 @@
+// #LAYOUT# M65 KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Automatic switching to legacy C64 mode if loading anything below $0800
+//
+
+#if CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO
+
+
+m65_load_autoswitch_tape:
+
+	lda VERCKK
+	bne m65_load_autoswitch_done       // no autoswitch for VERIFY
+
+	lda STAL+1
+
+#endif
+
+m65_load_autoswitch:
+
+	lda VERCKK
+	bne m65_load_autoswitch_done       // no autoswitch for VERIFY
+
+	lda EAL+1
+
+	// FALLTROUGH
+
+m65_load_autoswitch_check:
+
+	cmp #$08
+	bcs m65_load_autoswitch_done       // no autoswitch if loading above $07FF
+
+	jsr M65_MODEGET
+	bcs m65_load_autoswitch_done       // no autoswitch if already in legacy mode
+
+	sec
+	jmp M65_MODESET
+
+	// XXX consider displaying something here
+
+m65_load_autoswitch_done:
+
+	rts
diff --git a/src/kernal/board_m65/mega65_proxies.s b/src/kernal/board_m65/mega65_proxies.s
index 51651693..2eb02bb8 100644
--- a/src/kernal/board_m65/mega65_proxies.s
+++ b/src/kernal/board_m65/mega65_proxies.s
@@ -53,6 +53,12 @@ proxy_K1_lvs_load_verify_error:
 	jsr map_NORMAL
 	jmp lvs_load_verify_error
 
+proxy_K1_m65_load_autoswitch_tape:
+
+	jsr map_NORMAL
+	jsr m65_load_autoswitch_tape
+	jmp_8 !-
+
 proxy_K1_print_kernal_message:
 
 	jsr map_NORMAL
diff --git a/src/kernal/iec/load_iec.s b/src/kernal/iec/load_iec.s
index c9778dd0..09d02bbd 100644
--- a/src/kernal/iec/load_iec.s
+++ b/src/kernal/iec/load_iec.s
@@ -95,7 +95,16 @@ load_iec:
 	lda STAL+1
 	sta EAL+1	
 !:
+#if ROM_LAYOUT_M65
+
+	// Switch to legacy mode if needed
+
+	jsr m65_load_autoswitch
+
+#endif
+
 	// Display start address
+
 	jsr lvs_display_loading_verifying
 
 #if (CONFIG_IEC_JIFFYDOS || CONFIG_IEC_DOLPHINDOS) && !CONFIG_MEMORY_MODEL_60K
diff --git a/src/kernal/tape/tape_common.s b/src/kernal/tape/tape_common.s
index e46ce6b1..4b896671 100644
--- a/src/kernal/tape/tape_common.s
+++ b/src/kernal/tape/tape_common.s
@@ -223,6 +223,14 @@ tape_handle_header:
 
 	jsr lvs_STAL_to_MEMUSS
 
+#if ROM_LAYOUT_M65
+
+	// Switch to legacy mode if needed
+
+	jsr m65_load_autoswitch_tape
+
+#endif
+
 	// Print LOADING and start address
 
 	jsr lvs_display_loading_verifying