From 6063d8e96f4b7c8f7097a0caede7d56ae18550c9 Mon Sep 17 00:00:00 2001
From: tomcw <tomcw@users.noreply.github.com>
Date: Sat, 18 Mar 2017 13:56:18 +0000
Subject: [PATCH] SSC: Experimental support for 6551's DTR via -dtr or
 -dtr-invert args (#386)

---
 source/Applewin.cpp    |  8 ++++++++
 source/SerialComms.cpp | 21 +++++++++++++++++----
 source/SerialComms.h   |  6 ++++++
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/source/Applewin.cpp b/source/Applewin.cpp
index 119e782a..c1d76cf6 100644
--- a/source/Applewin.cpp
+++ b/source/Applewin.cpp
@@ -1034,6 +1034,14 @@ int APIENTRY WinMain(HINSTANCE passinstance, HINSTANCE, LPSTR lpCmdLine, int)
 		{
 			g_bMultiMon = true;
 		}
+		else if (strcmp(lpCmdLine, "-dtr") == 0)	// GH#386
+		{
+			sg_SSC.SupportDTR(true, false);
+		}
+		else if (strcmp(lpCmdLine, "-dtr-invert") == 0)	// GH#386
+		{
+			sg_SSC.SupportDTR(true, true);
+		}
 		else	// unsupported
 		{
 			LogFileOutput("Unsupported arg: %s\n", lpCmdLine);
diff --git a/source/SerialComms.cpp b/source/SerialComms.cpp
index 5aa1f209..f45743f3 100644
--- a/source/SerialComms.cpp
+++ b/source/SerialComms.cpp
@@ -74,7 +74,9 @@ SSC_DIPSW CSuperSerialCard::m_DIPSWDefault =
 CSuperSerialCard::CSuperSerialCard() :
 	m_aySerialPortChoices(NULL),
 	m_uTCPChoiceItemIdx(0),
-	m_uSlot(0)
+	m_uSlot(0),
+	m_bCfgSupportDTR(false),	// GH#386 - don't support by default until we have confirmed it works
+	m_bCfgInvertDTR(false)
 {
 	memset(m_ayCurrentSerialPortName, 0, sizeof(m_ayCurrentSerialPortName));
 	m_dwSerialPortItem = 0;
@@ -111,6 +113,8 @@ void CSuperSerialCard::InternalReset()
 	m_qComSerialBuffer[0].clear();
 	m_qComSerialBuffer[1].clear();
 	m_qTcpSerialBuffer.clear();
+
+	m_uDTR = DTR_CONTROL_DISABLE;
 }
 
 CSuperSerialCard::~CSuperSerialCard()
@@ -212,6 +216,7 @@ void CSuperSerialCard::UpdateCommState()
 	dcb.ByteSize = m_uByteSize;
 	dcb.Parity   = m_uParity;
 	dcb.StopBits = m_uStopBits;
+	dcb.fDtrControl = m_uDTR;
 
 	SetCommState(m_hCommHandle,&dcb);
 }
@@ -511,10 +516,18 @@ BYTE __stdcall CSuperSerialCard::CommCommand(WORD, WORD, BYTE write, BYTE value,
 		// interrupt request disable [0=enable receiver interrupts] - NOTE: SSC docs get this wrong!
 		m_bRxIrqEnabled = ((m_uCommandByte & 0x02) == 0);
 
-		if (m_uCommandByte	& 0x01)	// Data Terminal Ready (DTR) setting [0=set DTR high (indicates 'not ready')]
+		if (m_bCfgSupportDTR)	// GH#386
 		{
-			// Note that, although the DTR is generally not used in the SSC (it may actually not
-			// be connected!), it must be set to 'low' in order for the 6551 to function correctly.
+			// Legacy comment - inaccurate? (see docs\SSC Memory Locations for Programmers.txt)
+			// . Note that, although the DTR is generally not used in the SSC (it may actually not be connected!),
+			//   it must be set to 'low' in order for the 6551 to function correctly.
+
+			// Data Terminal Ready (DTR) setting [0=set DTR high (indicates 'not ready')]
+			const bool bDTR_Ready = (m_uCommandByte & 0x01) ? true : false;
+			if (bDTR_Ready)
+				m_uDTR = !m_bCfgInvertDTR ? DTR_CONTROL_ENABLE : DTR_CONTROL_DISABLE;
+			else
+				m_uDTR = !m_bCfgInvertDTR ? DTR_CONTROL_DISABLE : DTR_CONTROL_ENABLE;
 		}
 
 		UpdateCommState();
diff --git a/source/SerialComms.h b/source/SerialComms.h
index c86678d2..036486bb 100644
--- a/source/SerialComms.h
+++ b/source/SerialComms.h
@@ -43,6 +43,7 @@ public:
 	char*	GetSerialPortName() { return m_ayCurrentSerialPortName; }
 	void	SetSerialPortName(const char* pSerialPortName);
 	bool	IsActive() { return (m_hCommHandle != INVALID_HANDLE_VALUE) || (m_hCommListenSocket != INVALID_SOCKET); }
+	void	SupportDTR(bool bEnable, bool bInvert) { m_bCfgSupportDTR = bEnable; m_bCfgInvertDTR = bInvert; }
 
 	void	CommTcpSerialAccept();
 	void	CommTcpSerialReceive();
@@ -139,4 +140,9 @@ private:
 
 	BYTE* m_pExpansionRom;
 	UINT m_uSlot;
+
+	// DTR
+	UINT	m_uDTR;
+	bool m_bCfgSupportDTR;
+	bool m_bCfgInvertDTR;
 };