pi1541/iec_bus.cpp

// Pi1541 - A Commodore 1541 disk drive emulator
// Copyright(C) 2018 Stephen White
//
// This file is part of Pi1541.
// 
// Pi1541 is free software : you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// Pi1541 is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with Pi1541. If not, see <http://www.gnu.org/licenses/>.

#include "iec_bus.h"

u32 IEC_Bus::PIGPIO_MASK_IN_ATN = 1 << PIGPIO_ATN;
u32 IEC_Bus::PIGPIO_MASK_IN_DATA = 1 << PIGPIO_DATA;
u32 IEC_Bus::PIGPIO_MASK_IN_CLOCK = 1 << PIGPIO_CLOCK;
u32 IEC_Bus::PIGPIO_MASK_IN_SRQ = 1 << PIGPIO_SRQ;
u32 IEC_Bus::PIGPIO_MASK_IN_RESET = 1 << PIGPIO_RESET;

bool IEC_Bus::PI_Atn = false;
bool IEC_Bus::PI_Data = false;
bool IEC_Bus::PI_Clock = false;
bool IEC_Bus::PI_Reset = false;

bool IEC_Bus::VIA_Atna = false;
bool IEC_Bus::VIA_Data = false;
bool IEC_Bus::VIA_Clock = false;

bool IEC_Bus::DataSetToOut = false;
bool IEC_Bus::AtnaDataSetToOut = false;
bool IEC_Bus::ClockSetToOut = false;

bool IEC_Bus::OutputLED = false;
bool IEC_Bus::OutputSound = false;

bool IEC_Bus::Resetting = false;

bool IEC_Bus::splitIECLines = false;
bool IEC_Bus::invertIECInputs = false;

u32 IEC_Bus::myOutsGPFSEL1 = 0;
u32 IEC_Bus::myOutsGPFSEL0 = 0;
bool IEC_Bus::InputButton[5];
bool IEC_Bus::InputButtonPrev[5];
u32 IEC_Bus::validInputCount[5];
u32 IEC_Bus::inputRepeatThreshold[5];
u32 IEC_Bus::inputRepeat[5];
u32 IEC_Bus::inputRepeatPrev[5];

m6522* IEC_Bus::VIA = 0;

void IEC_Bus::Read(void)
{
	IOPort* portB = 0;
	unsigned gplev0 = read32(ARM_GPIO_GPLEV0);

	int index;
	int buttonCount = sizeof(ButtonPinFlags) / sizeof(unsigned);
	for (index = 0; index < buttonCount; ++index)
	{
		UpdateButton(index, gplev0);
	}

	if (VIA) portB = VIA->GetPortB();

	bool ATNIn = (gplev0 & PIGPIO_MASK_IN_ATN) == (invertIECInputs ? PIGPIO_MASK_IN_ATN : 0);
	if (PI_Atn != ATNIn)
	{
		PI_Atn = ATNIn;

		if (VIA)
		{
			if ((portB->GetDirection() & 0x10) != 0)
			{
				// Emulate the XOR gate UD3
				// We only need to do this when fully emulating, iec commands do this internally
				AtnaDataSetToOut = (VIA_Atna != PI_Atn);
			}

			portB->SetInput(VIAPORTPINS_ATNIN, ATNIn);	//is inverted and then connected to pb7 and ca1
			VIA->InputCA1(ATNIn);
		}
	}

	if (portB && (portB->GetDirection() & 0x10) == 0)
		AtnaDataSetToOut = false; // If the ATNA PB4 gets set to an input then we can't be pulling data low. (Maniac Mansion does this)

	if (!AtnaDataSetToOut && !DataSetToOut)	// only sense if we have not brought the line low (because we can't as we have the pin set to output but we can simulate in software)
	{
		bool DATAIn = (gplev0 & PIGPIO_MASK_IN_DATA) == (invertIECInputs ? PIGPIO_MASK_IN_DATA : 0);
		if (PI_Data != DATAIn)
		{
			PI_Data = DATAIn;
			if (VIA) portB->SetInput(VIAPORTPINS_DATAIN, DATAIn);	// VIA DATAin pb0 output from inverted DIN 5 DATA
		}
	}
	else
	{
		PI_Data = true;
		if (VIA) portB->SetInput(VIAPORTPINS_DATAIN, true);	// simulate the read in software
	}

	if (!ClockSetToOut)	// only sense if we have not brought the line low (because we can't as we have the pin set to output but we can simulate in software)
	{
		bool CLOCKIn = (gplev0 & PIGPIO_MASK_IN_CLOCK) == (invertIECInputs ? PIGPIO_MASK_IN_CLOCK  : 0);
		if (PI_Clock != CLOCKIn)
		{
			PI_Clock = CLOCKIn;
			if (VIA) portB->SetInput(VIAPORTPINS_CLOCKIN, CLOCKIn); // VIA CLKin pb2 output from inverted DIN 4 CLK
		}
	}
	else
	{
		PI_Clock = true;
		if (VIA) portB->SetInput(VIAPORTPINS_CLOCKIN, true); // simulate the read in software
	}

	Resetting = (gplev0 & PIGPIO_MASK_IN_RESET) == (invertIECInputs ? PIGPIO_MASK_IN_RESET : 0);
}