From 9d55740a0f84b090b3e62368e99733f85400c051 Mon Sep 17 00:00:00 2001
From: folkert van heusden <mail@vanheusden.com>
Date: Sat, 18 Jun 2022 08:48:29 +0200
Subject: [PATCH] SR0 errors by KKTBD0 fixed

---
 bus.cpp | 19 ++++++++++++++++++-
 bus.h   |  1 +
 cpu.cpp |  7 +++++--
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/bus.cpp b/bus.cpp
index 446b244..e3cb197 100644
--- a/bus.cpp
+++ b/bus.cpp
@@ -326,6 +326,14 @@ void bus::setMMR0Bit(const int bit)
 	MMR0 |= 1 << bit;
 }
 
+void bus::clearMMR0Bit(const int bit)
+{
+	assert(bit != 10 && bit != 11);
+	assert(bit < 16 && bit >= 0);
+
+	MMR0 &= ~(1 << bit);
+}
+
 void bus::setMMR2(const uint16_t value) 
 {
 	MMR2 = value;
@@ -359,6 +367,7 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 
 					pages[run_mode][0][apf].pdr |= 1 << 7;  // TODO: D/I
 
+					MMR0 &= 017777;
 					MMR0 |= 1 << 13;  // read-only
 
 					MMR0 &= ~(3 << 5);
@@ -367,6 +376,8 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 					MMR0 &= ~14;  // add current page
 					MMR0 |= apf << 1;
 
+					DOLOG(info, true, "MMR0: %06o", MMR0);
+
 					throw 1;
 				}
 				else if (!is_write) { // read
@@ -377,7 +388,11 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 
 						pages[run_mode][0][apf].pdr |= 1 << 7;  // TODO: D/I
 
-						MMR0 |= 1 << 13;  // read-only
+						MMR0 &= 017777;
+						if (access_control == 0 || access_control == 4)
+							MMR0 |= 1 << 15;  // not resident
+						else
+							MMR0 |= 1 << 13;  // read-only
 
 						MMR0 &= ~(3 << 5);
 						MMR0 |= run_mode << 5;
@@ -398,6 +413,7 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 				DOLOG(debug, !peek_only, "bus::calculate_physical_address %o >= %o", m_offset, n_pages * 8192);
 				DOLOG(info, true, "TRAP(04) (throw 3) on address %06o", a);
 
+				MMR0 &= 017777;
 				MMR0 |= 1 << 15;  // non-resident
 
 				MMR0 &= ~14;  // add current page
@@ -415,6 +431,7 @@ uint32_t bus::calculate_physical_address(const int run_mode, const uint16_t a, c
 				DOLOG(info, true, "TRAP(0250) (throw 4) on address %06o", a);
 				c->schedule_trap(0250);  // invalid access
 
+				MMR0 &= 017777;
 				MMR0 |= 1 << 14;  // length
 
 				MMR0 &= ~14;  // add current page
diff --git a/bus.h b/bus.h
index ba06211..b4c92d5 100644
--- a/bus.h
+++ b/bus.h
@@ -85,6 +85,7 @@ public:
 	void     addToMMR1(const int8_t delta, const uint8_t reg);
 	void     setMMR0(int value);
 	void     setMMR0Bit(const int bit);
+	void     clearMMR0Bit(const int bit);
 	void     setMMR2(const uint16_t value);
 
 	uint16_t get_switch_register() const { return switch_register; }
diff --git a/cpu.cpp b/cpu.cpp
index a8243b8..44b79a6 100644
--- a/cpu.cpp
+++ b/cpu.cpp
@@ -1647,6 +1647,7 @@ void cpu::schedule_trap(const uint16_t vector)
 	scheduled_trap = vector;
 }
 
+// 'is_interrupt' is not correct naming; it is true for mmu faults and interrupts
 void cpu::trap(const uint16_t vector, const int new_ipl, const bool is_interrupt)
 {
 	uint16_t before_psw = getPSW();
@@ -1661,7 +1662,9 @@ void cpu::trap(const uint16_t vector, const int new_ipl, const bool is_interrupt
 		b->addToMMR1(-2, 6);
 	}
 
-	if (!is_interrupt)
+	if (is_interrupt)
+		b->clearMMR0Bit(12);
+	else
 		b->setMMR0Bit(12);  // it's a trap
 
 	setPC(b->readWord(vector + 0));
@@ -2156,7 +2159,7 @@ void cpu::step_a()
 		b->clearMMR1();
 
 	if (scheduled_trap) {
-		trap(scheduled_trap, 7);
+		trap(scheduled_trap, 7, true);
 
 		scheduled_trap = 0;