mirror of
https://github.com/TomHarte/CLK.git
synced 2024-11-30 04:50:08 +00:00
117 lines
4.3 KiB
C++
117 lines
4.3 KiB
C++
//
|
|
// Card.h
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 23/04/2018.
|
|
// Copyright 2018 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#ifndef Card_h
|
|
#define Card_h
|
|
|
|
#include "../../../Processors/6502/6502.hpp"
|
|
#include "../../../ClockReceiver/ClockReceiver.hpp"
|
|
#include "../../../Activity/Observer.hpp"
|
|
|
|
namespace Apple::II {
|
|
|
|
/*!
|
|
This provides a small subset of the interface offered to cards installed in
|
|
an Apple II, oriented pragmatically around the cards that are implemented.
|
|
|
|
The main underlying rule is as it is elsewhere in the emulator: no
|
|
_inaccurate_ simplifications — no provision of information that shouldn't
|
|
actually commute, no interfaces that say they do one thing but which by both
|
|
both sides are coupled through an unwritten understanding of abuse.
|
|
|
|
Special notes:
|
|
|
|
Devices that announce a select constraint, being interested in acting only
|
|
when their IO or Device select is active will receive just-in-time @c run_for
|
|
notifications, as well as being updated at the end of each of the Apple's
|
|
@c run_for periods, prior to a @c flush.
|
|
|
|
Devices that do not announce a select constraint will prima facie receive a
|
|
@c perform_bus_operation every cycle. They'll also receive a @c flush.
|
|
It is **highly** recomended that such devices also implement @c Sleeper
|
|
as they otherwise prima facie require a virtual method call every
|
|
single cycle.
|
|
*/
|
|
class Card {
|
|
public:
|
|
virtual ~Card() {}
|
|
enum Select: int {
|
|
None = 0, // No select line is active.
|
|
IO = 1 << 0, // IO select is active; i.e. access is in range $C0x0 to $C0xf.
|
|
Device = 1 << 1, // Device select is active; i.e. access is in range $Cx00 to $Cxff.
|
|
|
|
C8Region = 1 << 2, // Access is to the region $c800 to $cfff, was preceded by at least
|
|
// one Device access to this card, and has not yet been followed up
|
|
// by an access to $cfff.
|
|
};
|
|
|
|
/*!
|
|
Advances time by @c cycles, of which @c stretches were stretched.
|
|
|
|
This is posted only to cards that announced a select constraint. Cards with
|
|
no constraints, that want to be informed of every machine cycle, will receive
|
|
a call to perform_bus_operation every cycle and should use that for time keeping.
|
|
*/
|
|
virtual void run_for([[maybe_unused]] Cycles cycles, [[maybe_unused]] int stretches) {}
|
|
|
|
/// Requests a flush of any pending audio or video output.
|
|
virtual void flush() {}
|
|
|
|
/*!
|
|
Performs a bus operation.
|
|
|
|
@param select The state of the card's select lines: indicates whether the Apple II
|
|
thinks this card should respond as though this were an IO access, a Device access,
|
|
or it thinks that the card shouldn't respond.
|
|
@param is_read @c true if this is a read cycle; @c false otherwise.
|
|
@param address The current value of the address bus.
|
|
@param value A pointer to the value of the data bus, not accounting input from cards.
|
|
If this is a read cycle, the card is permitted to replace this value with the value
|
|
output by the card, if any. If this is a write cycle, the card should only read
|
|
this value.
|
|
*/
|
|
virtual void perform_bus_operation(Select select, bool is_read, uint16_t address, uint8_t *value) = 0;
|
|
|
|
/*!
|
|
Returns the type of bus selects this card is actually interested in.
|
|
As specified, the default is that cards will ask to receive perform_bus_operation
|
|
only when their select lines are active.
|
|
|
|
There's a substantial caveat here: cards that register to receive @c None
|
|
will receive a perform_bus_operation every cycle. To reduce the number of
|
|
virtual method calls, they **will not** receive run_for. run_for will propagate
|
|
only to cards that register for IO and/or Device accesses only.
|
|
*/
|
|
int get_select_constraints() const {
|
|
return select_constraints_;
|
|
}
|
|
|
|
/*! Cards may supply a target for activity observation if desired. */
|
|
virtual void set_activity_observer([[maybe_unused]] Activity::Observer *observer) {}
|
|
|
|
struct Delegate {
|
|
virtual void card_did_change_select_constraints(Card *card) = 0;
|
|
};
|
|
void set_delegate(Delegate *delegate) {
|
|
delegate_ = delegate;
|
|
}
|
|
|
|
protected:
|
|
int select_constraints_ = IO | Device;
|
|
Delegate *delegate_ = nullptr;
|
|
void set_select_constraints(int constraints) {
|
|
if(constraints == select_constraints_) return;
|
|
select_constraints_ = constraints;
|
|
if(delegate_) delegate_->card_did_change_select_constraints(this);
|
|
}
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* Card_h */
|