From aaca51494ad141a0c0918137b61db85e076c1e9d Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Sun, 1 Dec 2019 17:18:06 +0100
Subject: [PATCH] fix broken IEC flush with JiffyDOS

---
 c64/kernal/iec_fast/iec_rx_byte_jiffydos.s | 4 ++++
 c64/kernal/iec_fast/iec_tx_byte_jiffydos.s | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/c64/kernal/iec_fast/iec_rx_byte_jiffydos.s b/c64/kernal/iec_fast/iec_rx_byte_jiffydos.s
index 9cb648bd..f7c78ecb 100644
--- a/c64/kernal/iec_fast/iec_rx_byte_jiffydos.s
+++ b/c64/kernal/iec_fast/iec_rx_byte_jiffydos.s
@@ -84,6 +84,10 @@ iec_rx_byte_jiffydos:
 	bmi !+
 	jsr kernalstatus_EOI
 !:
+	// Indicate that no byte waits in output buffer
+	lda #$00
+	sta C3PO
+
 	// Restore proper IECPROTO value
 	lda #$01
 	sta IECPROTO
diff --git a/c64/kernal/iec_fast/iec_tx_byte_jiffydos.s b/c64/kernal/iec_fast/iec_tx_byte_jiffydos.s
index 7903e333..26b15c27 100644
--- a/c64/kernal/iec_fast/iec_tx_byte_jiffydos.s
+++ b/c64/kernal/iec_fast/iec_tx_byte_jiffydos.s
@@ -77,6 +77,10 @@ iec_tx_byte_jiffydos_finalize:
 	ora #BIT_CIA2_PRA_CLK_OUT          // pull CLK
 	sta CIA2_PRA
 
+	// Indicate that no byte waits in output buffer
+	lda #$00
+	sta C3PO
+
 	// Restore proper IECPROTO value
 	lda #$01
 	sta IECPROTO