started work on better JiffyDOS LOAD routine

c64/kernal/iec_fast/jiffydos_load.s

@@ -6,7 +6,6 @@
 // JiffyDOS protocol support for IEC - optimized load loop
 //
 
-
 #if CONFIG_IEC_JIFFYDOS && !CONFIG_MEMORY_MODEL_60K
 
 
@@ -20,12 +19,88 @@
 
 jiffydos_load:
 
+/* XXX NEW version, not yet finished
+
+	//
+	// JiffyDOS protocol support for IEC - optimized load loop
+	//
+	// Based on description from https://github.com/mist64/cbmbus_doc
+	//
+
+	// First we need to switch the device to optimized LOAD protocol,
+	// by making it talk on channel 1 instead of 0
+
+	jsr UNTLK
+
+	lda FA
+	jsr TALK
+	// XXX bcs load_iec_err
+
+	lda #$61 // ask to talk on channel 1
+	sta TBTCNT
+	jsr iec_tx_command
+	// XXX bcs load_iec_error
+	// XXX if not on JiffyDOS protoccol, report error
+
 	// Timing is critical, do not allow interrupts
 	sei
 
 #if CONFIG_IEC_JIFFYDOS_BLANK
 
-	// Preserve register with screen status (blank/visibe)
+	// Preserve register with screen status (blank/visible)
+	lda VIC_SCROLY
+	sta TBTCNT
+
+	// Blank screen to make sure no sprite/badline will interrupt
+	jsr screen_off
+
+#else
+
+	// Store previous sprite status in temporary variable
+	jsr jiffydos_prepare
+	sta TBTCNT
+
+#endif
+
+	// FALLTROUGH
+
+jiffydos_load_mode_escape:
+
+	// We are now in escape mode - release DATA so that we can read it
+	jsr iec_release_clk_data // XXX maybe release just data?
+
+	// Wait till device tells us whether this is EOI/error
+	jsr iec_wait_for_clk_release
+
+	// Check DATA line - if pulled, there is more data
+	bit CIA2_PRA
+	bpl jiffydos_load_mode_receive
+
+	// XXX check for error
+
+
+
+jiffydos_load_mode_receive:
+
+
+	// Preserve 3 lowest bits of CIA2_PRA  XXX deduplicate this
+
+	lda CIA2_PRA
+	and #%00000111
+	sta C3PO
+
+	// XXX read data
+
+*/
+
+
+
+	// Timing is critical, do not allow interrupts
+	sei
+
+#if CONFIG_IEC_JIFFYDOS_BLANK
+
+	// Preserve register with screen status (blank/visible)
 	lda VIC_SCROLY
 	sta TBTCNT