mirror of https://github.com/stella-emu/stella.git
Cleaned up the RIOT class a little more, hopefully making it easier to
understand. Eliminated certains constants that I could never really explain (like the 0x40000 constant from z26), and more properly emulated the behaviour when going negative on the timer count (according to the documentation). git-svn-id: svn://svn.code.sf.net/p/stella/code/trunk@1483 8b62c5a3-ac7e-4cc8-8f21-d9a121418aba
This commit is contained in:
stephena
parent
0682a85999
commit
74362c3f0f
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@ -13,7 +13,7 @@
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// See the file "license" for information on usage and redistribution of
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// this file, and for a DISCLAIMER OF ALL WARRANTIES.
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//
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// $Id: M6532.cxx,v 1.20 2008-04-20 19:52:33 stephena Exp $
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// $Id: M6532.cxx,v 1.21 2008-04-23 16:51:11 stephena Exp $
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//============================================================================
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#include <assert.h>
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@ -55,15 +55,14 @@ void M6532::reset()
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myTimer = 25 + (random.next() % 75);
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myIntervalShift = 6;
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myCyclesWhenTimerSet = 0;
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myTimerReadAfterInterrupt = false;
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myInterruptEnabled = false;
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myInterruptTriggered = false;
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// Zero the I/O registers
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myOutA = 0x00;
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myDDRA = 0x00;
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myDDRB = 0x00;
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myDDRA = myDDRB = myOutA = 0x00;
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// Zero the timer registers
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myOutTimer[0] = myOutTimer[1] = myOutTimer[2] = myOutTimer[3] = 0x0;
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myOutTimer[0] = myOutTimer[1] = myOutTimer[2] = myOutTimer[3] = 0x00;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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@ -161,30 +160,26 @@ uInt8 M6532::peek(uInt16 addr)
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case 0x04: // Timer Output
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case 0x06:
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{
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uInt32 timer = timerClocks();
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myInterruptTriggered = false;
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Int32 timer = timerClocks();
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// See if the timer has expired yet?
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// Note that this constant comes from z26, and corresponds to
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// 256 intervals of T1024T (ie, the maximum that the timer
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// should hold)
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if(!(timer & 0x40000))
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if(timer >= 0)
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{
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return (timer >> myIntervalShift) & 0xff;
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return (uInt8)(timer >> myIntervalShift);
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}
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else
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{
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myTimerReadAfterInterrupt = true;
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return timer & 0xff;
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if(timer != -1)
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myInterruptTriggered = true;
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return (uInt8)(timer >= -256 ? timer : 0);
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}
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}
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case 0x05: // Interrupt Flag
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case 0x07:
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{
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// TODO - test this
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// it seems as if myTimerReadAfterInterrupt being true
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// would mean that the interrupt has been enabled??
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if((timerClocks() >= 0) || myTimerReadAfterInterrupt)
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if((timerClocks() >= 0) || myInterruptEnabled && myInterruptTriggered)
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return 0x00;
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else
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return 0x80;
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@ -210,122 +205,93 @@ void M6532::poke(uInt16 addr, uInt8 value)
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if((addr & 0x1080) == 0x0080 && (addr & 0x0200) == 0x0000)
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{
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myRAM[addr & 0x007f] = value;
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return;
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}
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else if((addr & 0x07) == 0x00) // Port A I/O Register (Joystick)
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{
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myOutA = value;
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uInt8 a = myOutA & myDDRA;
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Controller& port0 = myConsole.controller(Controller::Left);
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port0.write(Controller::One, a & 0x10);
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port0.write(Controller::Two, a & 0x20);
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port0.write(Controller::Three, a & 0x40);
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port0.write(Controller::Four, a & 0x80);
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Controller& port1 = myConsole.controller(Controller::Right);
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port1.write(Controller::One, a & 0x01);
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port1.write(Controller::Two, a & 0x02);
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port1.write(Controller::Three, a & 0x04);
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port1.write(Controller::Four, a & 0x08);
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}
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else if((addr & 0x07) == 0x01) // Port A Data Direction Register
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// A2 Distingusishes I/O registers from the timer
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if((addr & 0x04) != 0)
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{
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myDDRA = value;
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uInt8 a = myOutA | ~myDDRA;
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// TODO - Fix this properly in the core
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// Any time the core code needs to know what type of controller
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// is connected, it's by definition a bug
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// A real Atari doesn't 'know' that an AVox is connected, so we
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// shouldn't either
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/*
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20060608 bkw: Not the most elegant thing in the world...
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When a bit in the DDR is set as input, +5V is placed on its output
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pin. When it's set as output, either +5V or 0V (depending on the
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contents of SWCHA) will be placed on the output pin.
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The standard macros for the AtariVox use this fact to send data
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to the port.
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This code isn't 100% correct: it assumes the SWCHA bits are all 0.
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This is good enough to emulate the AtariVox, if the programmer is
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using SWACNT to do output (e.g. the SPKOUT macro from speakjet.inc)
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and if he's leaving SWCHA alone.
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The inaccuracy here means that wrongly-written code will still
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be able to drive the emulated AtariVox, even though it wouldn't
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work on real hardware.
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*/
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Controller& port0 = myConsole.controller(Controller::Left);
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port0.write(Controller::One, a & 0x10);
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port0.write(Controller::Two, a & 0x20);
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port0.write(Controller::Three, a & 0x40);
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port0.write(Controller::Four, a & 0x80);
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Controller& port1 = myConsole.controller(Controller::Right);
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port1.write(Controller::One, a & 0x01);
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port1.write(Controller::Two, a & 0x02);
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port1.write(Controller::Three, a & 0x04);
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port1.write(Controller::Four, a & 0x08);
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}
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else if((addr & 0x07) == 0x02) // Port B I/O Register (Console switches)
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{
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return; // hardwired as read-only
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}
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else if((addr & 0x07) == 0x03) // Port B Data Direction Register
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{
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return; // hardwired as read-only
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}
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else if((addr & 0x17) == 0x14) // Write timer divide by 1
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{
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myOutTimer[0] = value;
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myIntervalShift = 0;
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myTimer = myOutTimer[0] << myIntervalShift;
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myCyclesWhenTimerSet = mySystem->cycles();
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myTimerReadAfterInterrupt = false;
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}
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else if((addr & 0x17) == 0x15) // Write timer divide by 8
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{
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myOutTimer[1] = value;
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myIntervalShift = 3;
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myTimer = myOutTimer[1] << myIntervalShift;
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myCyclesWhenTimerSet = mySystem->cycles();
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myTimerReadAfterInterrupt = false;
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}
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else if((addr & 0x17) == 0x16) // Write timer divide by 64
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{
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myOutTimer[2] = value;
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myIntervalShift = 6;
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myTimer = myOutTimer[2] << myIntervalShift;
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myCyclesWhenTimerSet = mySystem->cycles();
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myTimerReadAfterInterrupt = false;
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}
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else if((addr & 0x17) == 0x17) // Write timer divide by 1024
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{
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myOutTimer[3] = value;
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myIntervalShift = 10;
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myTimer = myOutTimer[3] << myIntervalShift;
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myCyclesWhenTimerSet = mySystem->cycles();
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myTimerReadAfterInterrupt = false;
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}
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else if((addr & 0x14) == 0x04) // Write Edge Detect Control
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{
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#ifdef DEBUG_ACCESSES
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cerr << "M6532 Poke (Write Edge Detect): "
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<< ((addr & 0x02) ? "PA7 enabled" : "PA7 disabled")
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<< ", "
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<< ((addr & 0x01) ? "Positive edge" : "Negative edge")
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<< endl;
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#endif
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if((addr & 0x10) != 0)
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{
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myInterruptEnabled = (addr & 0x08);
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setTimerRegister(value, addr & 0x03);
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}
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}
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else
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{
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#ifdef DEBUG_ACCESSES
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cerr << "BAD M6532 Poke: " << hex << addr << endl;
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#endif
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switch(addr & 0x03)
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{
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case 0: // Port A I/O Register (Joystick)
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{
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myOutA = value;
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uInt8 a = myOutA & myDDRA;
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Controller& port0 = myConsole.controller(Controller::Left);
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port0.write(Controller::One, a & 0x10);
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port0.write(Controller::Two, a & 0x20);
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port0.write(Controller::Three, a & 0x40);
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port0.write(Controller::Four, a & 0x80);
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Controller& port1 = myConsole.controller(Controller::Right);
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port1.write(Controller::One, a & 0x01);
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port1.write(Controller::Two, a & 0x02);
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port1.write(Controller::Three, a & 0x04);
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port1.write(Controller::Four, a & 0x08);
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break;
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}
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case 1: // Port A Data Direction Register
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{
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myDDRA = value;
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/*
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Undocumented feature used by the AtariVox and SaveKey.
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When the DDR is changed, the ORA (output register A) cached
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from a previous write to SWCHA is 'applied' to the controller pins.
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When a bit in the DDR is set as input, +5V is placed on its output
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pin. When it's set as output, either +5V or 0V (depending on the
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contents of SWCHA) will be placed on the output pin.
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The standard macros for the AtariVox use this fact to send data
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to the port. This is represented by the following algorithm:
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if(DDR bit is input) set output as 1
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else if(DDR bit is output) set output as bit in ORA
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*/
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uInt8 a = myOutA | ~myDDRA;
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Controller& port0 = myConsole.controller(Controller::Left);
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port0.write(Controller::One, a & 0x10);
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port0.write(Controller::Two, a & 0x20);
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port0.write(Controller::Three, a & 0x40);
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port0.write(Controller::Four, a & 0x80);
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Controller& port1 = myConsole.controller(Controller::Right);
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port1.write(Controller::One, a & 0x01);
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port1.write(Controller::Two, a & 0x02);
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port1.write(Controller::Three, a & 0x04);
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port1.write(Controller::Four, a & 0x08);
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break;
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}
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default: // Port B I/O & DDR Registers (Console switches)
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break; // hardwired as read-only
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}
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}
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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void M6532::setTimerRegister(uInt8 value, uInt8 interval)
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{
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static const uInt8 shift[] = { 0, 3, 6, 10 };
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myInterruptTriggered = false;
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myIntervalShift = shift[interval];
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myOutTimer[interval] = value;
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myTimer = value << myIntervalShift;
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myCyclesWhenTimerSet = mySystem->cycles();
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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bool M6532::save(Serializer& out) const
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{
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@ -343,10 +309,12 @@ bool M6532::save(Serializer& out) const
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out.putInt(myTimer);
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out.putInt(myIntervalShift);
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out.putInt(myCyclesWhenTimerSet);
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out.putBool(myTimerReadAfterInterrupt);
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out.putByte((char)myOutA);
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out.putBool(myInterruptEnabled);
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out.putBool(myInterruptTriggered);
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out.putByte((char)myDDRA);
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out.putByte((char)myDDRB);
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out.putByte((char)myOutA);
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out.putByte((char)myOutTimer[0]);
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out.putByte((char)myOutTimer[1]);
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out.putByte((char)myOutTimer[2]);
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@ -384,12 +352,12 @@ bool M6532::load(Deserializer& in)
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myTimer = (uInt32) in.getInt();
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myIntervalShift = (uInt32) in.getInt();
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myCyclesWhenTimerSet = (uInt32) in.getInt();
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myTimerReadAfterInterrupt = in.getBool();
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myInterruptEnabled = in.getBool();
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myInterruptTriggered = in.getBool();
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myOutA = (uInt8) in.getByte();
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myDDRA = (uInt8) in.getByte();
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myDDRB = (uInt8) in.getByte();
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myOutA = (uInt8) in.getByte();
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myOutTimer[0] = (uInt8) in.getByte();
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myOutTimer[1] = (uInt8) in.getByte();
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myOutTimer[2] = (uInt8) in.getByte();
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@ -13,7 +13,7 @@
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// See the file "license" for information on usage and redistribution of
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// this file, and for a DISCLAIMER OF ALL WARRANTIES.
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//
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// $Id: M6532.hxx,v 1.11 2008-04-20 19:52:33 stephena Exp $
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// $Id: M6532.hxx,v 1.12 2008-04-23 16:51:11 stephena Exp $
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//============================================================================
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#ifndef M6532_HXX
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@ -32,7 +32,7 @@ class Deserializer;
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RIOT
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@author Bradford W. Mott
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@version $Id: M6532.hxx,v 1.11 2008-04-20 19:52:33 stephena Exp $
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@version $Id: M6532.hxx,v 1.12 2008-04-23 16:51:11 stephena Exp $
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*/
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class M6532 : public Device
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{
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@ -130,6 +130,8 @@ class M6532 : public Device
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inline Int32 timerClocks()
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{ return myTimer - (mySystem->cycles() - myCyclesWhenTimerSet); }
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void setTimerRegister(uInt8 data, uInt8 interval);
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private:
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// Reference to the console
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const Console& myConsole;
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@ -146,11 +148,11 @@ class M6532 : public Device
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// Indicates the number of cycles when the timer was last set
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Int32 myCyclesWhenTimerSet;
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// Indicates if a read from timer has taken place after interrupt occured
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bool myTimerReadAfterInterrupt;
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// Indicates if a timer interrupt has been enabled
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bool myInterruptEnabled;
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// Last value written to Port A
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uInt8 myOutA;
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// Indicates if a read from timer has taken place after interrupt occured
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bool myInterruptTriggered;
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// Data Direction Register for Port A
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uInt8 myDDRA;
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@ -158,6 +160,9 @@ class M6532 : public Device
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// Data Direction Register for Port B
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uInt8 myDDRB;
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// Last value written to Port A
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uInt8 myOutA;
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// Last value written to the timer registers
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uInt8 myOutTimer[4];
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