From 36d803505e8ab2cd39cfa9e4fcf134e503cab6c5 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 28 Nov 2019 22:01:22 +0100
Subject: [PATCH] more work on JiffyDOS byte reception

---
 c64/kernal/iec/iec_jiffydos.s | 44 +++++++++++++++++++++++++----------
 c64/kernal/iec/iec_rx_byte.s  | 11 +++++----
 c64/kernal/iec/talk.s         |  2 ++
 3 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/c64/kernal/iec/iec_jiffydos.s b/c64/kernal/iec/iec_jiffydos.s
index 33331fad..e19795f8 100644
--- a/c64/kernal/iec/iec_jiffydos.s
+++ b/c64/kernal/iec/iec_jiffydos.s
@@ -3,7 +3,8 @@
 // JiffyDOS protocol support for IEC
 //
 
-// XXX finish this
+// XXX make it work
+// XXX split into multiple files
 
 
 
@@ -85,7 +86,18 @@ iec_tx_byte_jiffydos_finalize:
 	ora #BIT_CIA2_PRA_CLK_OUT          // pull CLK
 	sta CIA2_PRA
 
-	bne jiffydos_return_success        // branch always
+	// Restore proper IECPROTO value
+	lda #$01
+	sta IECPROTO
+
+	// Re-enable sprites and interrupts
+	pla
+	sta VIC_SPENA
+	cli
+
+	// Return success
+	jmp iec_return_success
+
 
 iec_tx_byte_jiffydos_wait_eoi:
 
@@ -154,26 +166,33 @@ iec_rx_byte_jiffydos:
 	eor C3PO
 	eor CIA2_PRA                       // bits 6 and 7 on CLK/DATA
 
+	// Preserve read byte
+	sta TBTCNT // $A4 is a byte buffer according to http://sta.c64.org/cbm64mem.html
+
+	// Retrieve status bits
+	lda CIA2_PRA
 	tax
 
-	// XXX CLK and DATA active = EOI
-	lda CIA2_PRA
-
-	// FALLTROUGH
-
-jiffydos_return_success:
+	// Pull DATA at the end
+	ora #BIT_CIA2_PRA_DAT_OUT
+	sta CIA2_PRA
 
+	// Check for EOI
+	txa
+	bmi !+
+	jsr kernalstatus_EOI
+!:
 	// Restore proper IECPROTO value
 	lda #$01
 	sta IECPROTO
 
-	// Re-enable sprites and interrupts
+	// Re-enable sprites
 	pla
 	sta VIC_SPENA
-	cli
 
-	// Return success
-	jmp iec_return_success
+	// End byte reception
+	jmp iec_rx_end
+
 
 
 jiffydos_wait_line:
@@ -198,6 +217,7 @@ jiffydos_wait_line_done:
 	rts
 
 
+
 jiffydos_prepare_for_transfer:
 
 	// We need to preserve 3 lowest bits of CIA2_PRA, they contain important
diff --git a/c64/kernal/iec/iec_rx_byte.s b/c64/kernal/iec/iec_rx_byte.s
index cd86f951..36f00f78 100644
--- a/c64/kernal/iec/iec_rx_byte.s
+++ b/c64/kernal/iec/iec_rx_byte.s
@@ -137,10 +137,13 @@ iec_rx_clk_wait2:
 	
 	// Restore registers
 	sta TBTCNT // $A4 is a byte buffer according to http://sta.c64.org/cbm64mem.html
-	pla
-	tay
-	pla
-	tax
+	
+	// FALLTROUGH
+
+iec_rx_end:
+
+	ply_trash_a
+	plx_trash_a
 	lda TBTCNT
 
 	clc
diff --git a/c64/kernal/iec/talk.s b/c64/kernal/iec/talk.s
index 52b689c3..76b83ff0 100644
--- a/c64/kernal/iec/talk.s
+++ b/c64/kernal/iec/talk.s
@@ -26,6 +26,8 @@ TALK:
 	// Encode and execute the command
 	ora #$40
 
+	// FALLTROUGH
+
 common_talk_listen: // common part of TALK and LISTEN
 
 	sta TBTCNT