From c733a4dbf8d1432df4e939343859db6a5db0f084 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 23 Jul 2021 21:58:52 -0400
Subject: [PATCH] Beefs up interrupt awareness.
---
Components/6526/6526.hpp | 1 +
.../Implementation/6526Implementation.hpp | 60 +++++++++++++++----
.../6526/Implementation/6526Storage.hpp | 5 +-
3 files changed, 53 insertions(+), 13 deletions(-)
diff --git a/Components/6526/6526.hpp b/Components/6526/6526.hpp
index 43a735f11..6026de66d 100644
--- a/Components/6526/6526.hpp
+++ b/Components/6526/6526.hpp
@@ -63,6 +63,7 @@ template <typename PortHandlerT, Personality personality> class MOS6526:
template <int port> void set_port_output();
template <int port> uint8_t get_port_input();
void update_interrupts();
+ void posit_interrupt(uint8_t mask);
};
}
diff --git a/Components/6526/Implementation/6526Implementation.hpp b/Components/6526/Implementation/6526Implementation.hpp
index 6cb226fd8..8a3571faf 100644
--- a/Components/6526/Implementation/6526Implementation.hpp
+++ b/Components/6526/Implementation/6526Implementation.hpp
@@ -27,8 +27,20 @@ template <int port> uint8_t MOS6526<BusHandlerT, personality>::get_port_input()
return (input & ~data_direction_[port]) | (output_[port] & data_direction_[port]);
}
+template <typename BusHandlerT, Personality personality>
+void MOS6526<BusHandlerT, personality>::posit_interrupt(uint8_t mask) {
+ interrupt_state_ |= mask;
+ update_interrupts();
+}
+
template <typename BusHandlerT, Personality personality>
void MOS6526<BusHandlerT, personality>::update_interrupts() {
+ if(interrupt_state_ & interrupt_control_) {
+ interrupt_state_ |= 0x80;
+
+ printf("6526 should signal interrupt\n");
+ assert(false);
+ }
}
template <typename BusHandlerT, Personality personality>
@@ -67,8 +79,12 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
// upon a write to the LSB.
case 8:
if constexpr (personality == Personality::P8250) {
- tod_ = (tod_ & 0xffff00) | uint32_t(value);
- tod_increment_mask_ = uint32_t(~0);
+ if(control_[1] & 0x80) {
+ tod_alarm_ = (tod_alarm_ & 0xffff00) | uint32_t(value);
+ } else {
+ tod_ = (tod_ & 0xffff00) | uint32_t(value);
+ tod_increment_mask_ = uint32_t(~0);
+ }
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
@@ -76,8 +92,12 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
break;
case 9:
if constexpr (personality == Personality::P8250) {
- tod_ = (tod_ & 0xff00ff) | uint32_t(value << 8);
- tod_increment_mask_ = 0;
+ if(control_[1] & 0x80) {
+ tod_alarm_ = (tod_alarm_ & 0xff00ff) | uint32_t(value << 8);
+ } else {
+ tod_ = (tod_ & 0xff00ff) | uint32_t(value << 8);
+ tod_increment_mask_ = 0;
+ }
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
@@ -85,8 +105,12 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
break;
case 10:
if constexpr (personality == Personality::P8250) {
- tod_ = (tod_ & 0x00ffff) | uint32_t(value << 16);
- tod_increment_mask_ = 0;
+ if(control_[1] & 0x80) {
+ tod_alarm_ = (tod_alarm_ & 0x00ffff) | uint32_t(value << 16);
+ } else {
+ tod_ = (tod_ & 0x00ffff) | uint32_t(value << 16);
+ tod_increment_mask_ = 0;
+ }
} else {
printf("6526 TOD clock not implemented\n");
assert(false);
@@ -101,10 +125,14 @@ void MOS6526<BusHandlerT, personality>::write(int address, uint8_t value) {
break;
// Interrupt control.
- case 13:
- interrupt_control_ = value;
+ case 13: {
+ if(interrupt_control_ & 0x80) {
+ interrupt_control_ |= value & 0x7f;
+ } else {
+ interrupt_control_ &= ~(value & 0x7f);
+ }
update_interrupts();
- break;
+ } break;
// Control.
case 14:
@@ -126,7 +154,6 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
switch(address) {
case 0: return get_port_input<0>();
case 1: return get_port_input<1>();
- case 13: return interrupt_control_;
case 2: case 3:
return data_direction_[address - 2];
@@ -137,6 +164,14 @@ uint8_t MOS6526<BusHandlerT, personality>::read(int address) {
case 6: return uint8_t(counters_[1].value >> 0);
case 7: return uint8_t(counters_[1].value >> 0);
+ // Interrupt state.
+ case 13: {
+ const uint8_t result = interrupt_state_;
+ interrupt_state_ = 0;
+ update_interrupts();
+ return result;
+ } break;
+
case 14: case 15:
return control_[address - 14];
@@ -211,14 +246,17 @@ void MOS6526<BusHandlerT, personality>::advance_tod(int count) {
if constexpr(personality == Personality::P8250) {
// The 8250 uses a simple binary counter to replace the
// 6526's time-of-day clock. So this is easy.
+ const uint32_t distance_to_alarm_ = (tod_alarm_ - tod_) & 0xffffff;
tod_ += uint32_t(count) & tod_increment_mask_;
+ if(distance_to_alarm_ <= uint32_t(count)) {
+ posit_interrupt(0x04);
+ }
} else {
// The 6526 uses a time-of-day clock. This may or may not
// be accurate.
}
}
-
}
}
diff --git a/Components/6526/Implementation/6526Storage.hpp b/Components/6526/Implementation/6526Storage.hpp
index 630e6e9af..8c76976de 100644
--- a/Components/6526/Implementation/6526Storage.hpp
+++ b/Components/6526/Implementation/6526Storage.hpp
@@ -17,14 +17,15 @@ struct MOS6526Storage {
uint8_t output_[2] = {0, 0};
uint8_t data_direction_[2] = {0, 0};
+
uint8_t interrupt_control_ = 0;
+ uint8_t interrupt_state_ = 0;
+
uint8_t control_[2] = {0, 0};
uint32_t tod_increment_mask_ = uint32_t(~0);
uint32_t tod_latch_ = 0;
uint32_t tod_ = 0;
-
- bool write_tod_alarm_ = false;
uint32_t tod_alarm_ = 0;
struct Counter {