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Ensures analogue channels which are already charging don't abide by c070.

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This commit is contained in:
Thomas Harte 2018-06-13 18:16:02 -04:00
parent f26e4734b3
commit 0be19d8de7
1 changed files with 30 additions and 5 deletions
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35
Machines/AppleII/AppleII.cpp
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@ -202,8 +202,25 @@ class ConcreteMachine:
bool buttons[3] = {false, false, false};
float axes[2] = {0.5f, 0.5f};
};
// On an Apple II, the programmer strobes 0xc070 and that causes each analogue input
// to begin a charge and discharge cycle **if they are not already charging**.
// The greater the analogue input, the faster they will charge and therefore the sooner
// they will discharge.
//
// This emulator models that with analogue_charge_ being essentially the amount of time,
// in charge threshold units, since 0xc070 was last strobed. But if any of the analogue
// inputs were already partially charged then they gain a bias in analogue_biases_.
//
// It's a little indirect, but it means only having to increment the one value in the
// main loop.
float analogue_charge_ = 0.0f;
float analogue_biases_[4] = {0.0f, 0.0f, 0.0f, 0.0f};
std::vector<std::unique_ptr<Inputs::Joystick>> joysticks_;
bool analogue_channel_is_discharged(size_t channel) {
return static_cast<Joystick *>(joysticks_[channel >> 1].get())->axes[channel & 1] < analogue_charge_ + analogue_biases_[channel];
}
public:
ConcreteMachine():
@ -431,7 +448,7 @@ class ConcreteMachine:
case 0xc067: { // Analogue input 3.
const size_t input = address - 0xc064;
*value &= 0x7f;
if(static_cast<Joystick *>(joysticks_[input >> 1].get())->axes[input & 1] < analogue_charge_) {
if(analogue_channel_is_discharged(input)) {
*value |= 0x80;
}
} break;
@ -441,6 +458,18 @@ class ConcreteMachine:
}
break;
case 0xc070: { // Permit analogue inputs that are currently discharged to begin a charge cycle.
// Ensure those that were still charging retain that state.
for(size_t c = 0; c < 4; ++c) {
if(analogue_channel_is_discharged(c)) {
analogue_biases_[c] = 0.0f;
} else {
analogue_biases_[c] += analogue_charge_;
}
}
analogue_charge_ = 0.0f;
} break;
/* Read-write switches. */
case 0xc050: update_video(); video_->set_graphics_mode(); break;
case 0xc051: update_video(); video_->set_text_mode(); break;
@ -451,10 +480,6 @@ class ConcreteMachine:
case 0xc056: update_video(); video_->set_low_resolution(); break;
case 0xc057: update_video(); video_->set_high_resolution(); break;
case 0xc070: // Reset analogue inputs.
analogue_charge_ = 0.0f;
break;
case 0xc010:
keyboard_input_ &= 0x7f;
if(string_serialiser_) {