From 2ba0364850d179a1c3afc372baeaff5462285ea8 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 8 May 2019 15:02:07 -0400
Subject: [PATCH] Adds the shift register interrupt.

---
 .../Implementation/6522Implementation.hpp     | 19 +++++++++++++++++--
 .../6522/Implementation/6522Storage.hpp       |  1 +
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Components/6522/Implementation/6522Implementation.hpp b/Components/6522/Implementation/6522Implementation.hpp
index 9dbdba037..7ae73cabf 100644
--- a/Components/6522/Implementation/6522Implementation.hpp
+++ b/Components/6522/Implementation/6522Implementation.hpp
@@ -84,7 +84,10 @@ template <typename T> void MOS6522<T>::set_register(int address, uint8_t value)
 		break;
 
 		// Shift
-		case 0xa:	registers_.shift = value;				break;
+		case 0xa:
+			registers_.shift = value;
+			shift_bits_remaining_ = 8;
+		break;
 
 		// Control
 		case 0xb:
@@ -175,7 +178,9 @@ template <typename T> uint8_t MOS6522<T>::get_register(int address) {
 		return registers_.timer[1] & 0x00ff;
 		case 0x9:	return registers_.timer[1] >> 8;
 
-		case 0xa:	return registers_.shift;
+		case 0xa:
+			shift_bits_remaining_ = 8;
+		return registers_.shift;
 
 		case 0xb:	return registers_.auxiliary_control;
 		case 0xc:	return registers_.peripheral_control;
@@ -363,11 +368,21 @@ template <typename T> void MOS6522<T>::set_control_line_output(Port port, Line l
 
 template <typename T> void MOS6522<T>::shift_in() {
 	registers_.shift = uint8_t((registers_.shift << 1) | (control_inputs_[1].lines[1] ? 1 : 0));
+	--shift_bits_remaining_;
+	if(!shift_bits_remaining_) {
+		registers_.interrupt_flags |= InterruptFlag::ShiftRegister;
+		reevaluate_interrupts();
+	}
 }
 
 template <typename T> void MOS6522<T>::shift_out() {
 	set_control_line_output(Port::B, Line::Two, registers_.shift & 0x80);
 	registers_.shift <<= 1;
+	--shift_bits_remaining_;
+	if(!shift_bits_remaining_) {
+		registers_.interrupt_flags |= InterruptFlag::ShiftRegister;
+		reevaluate_interrupts();
+	}
 }
 
 }
diff --git a/Components/6522/Implementation/6522Storage.hpp b/Components/6522/Implementation/6522Storage.hpp
index 66fa6e322..2a995c84a 100644
--- a/Components/6522/Implementation/6522Storage.hpp
+++ b/Components/6522/Implementation/6522Storage.hpp
@@ -50,6 +50,7 @@ class MOS6522Storage {
 
 		bool timer_is_running_[2] = {false, false};
 		bool last_posted_interrupt_status_ = false;
+		int shift_bits_remaining_ = 8;
 
 		enum InterruptFlag: uint8_t {
 			CA2ActiveEdge	= 1 << 0,