Change track and data registers for all drives together. When I imple…

…mented FDC, I did not know FDC was not aware of multiple drives and asumed one FDC could handle four drives, but one FDC can handle one drive at a time, and drive-selection is done outside of the FDC. This difference was not causing any known problem until now. But, you can break it in Dragon Slayer Legend of Heroes 1 Chapter 1 by saving data in the castle before the boss-battle, close Tsugaru, open again, and continue from the saved data.

src/diskdrive/diskdrive.cpp

@@ -1831,3 +1831,17 @@ void DiskDrive::SetSectorReg(int num)
 	state.drive[2]._sectorReg=num;
 	state.drive[3]._sectorReg=num;
 }
+void DiskDrive::SetTrackReg(int num)
+{
+	state.drive[0].trackReg=num;
+	state.drive[1].trackReg=num;
+	state.drive[2].trackReg=num;
+	state.drive[3].trackReg=num;
+}
+void DiskDrive::SetDataReg(int num)
+{
+	state.drive[0].dataReg=num;
+	state.drive[1].dataReg=num;
+	state.drive[2].dataReg=num;
+	state.drive[3].dataReg=num;
+}

src/diskdrive/diskdrive.h

@@ -364,6 +364,8 @@ class DiskDrive : public Device
 	int GetTrackReg(void) const;
 	int GetSectorReg(void) const;
 	int GetSectorReg(unsigned int drvSel) const;
+	void SetTrackReg(int num);
+	void SetDataReg(int num);
 	void SetSectorReg(int num);
 
 

src/towns/fdc/fdc.cpp

@@ -68,7 +68,7 @@ void TownsFDC::MakeReady(void)
 		townsPtr->UnscheduleDeviceCallBack(*this);
 		MakeReady();
 		drv.trackPos=0;
-		drv.trackReg=0;
+		SetTrackReg(0);
 		break;
 	case 0x10: // Seek
 		townsPtr->UnscheduleDeviceCallBack(*this);
@@ -85,7 +85,7 @@ void TownsFDC::MakeReady(void)
 		drv.trackPos=drv.dataReg;
 		if(state.lastCmd&0x10)
 		{
-			drv.trackReg=drv.trackPos;
+			SetTrackReg(drv.trackPos);
 		}
 		break;
 	case 0x20: // Step?
@@ -103,7 +103,7 @@ void TownsFDC::MakeReady(void)
 		}
 		if(state.lastCmd&0x10)
 		{
-			drv.trackReg=drv.trackPos;
+			SetTrackReg(drv.trackPos);
 		}
 		break;
 	case 0x40: // Step In
@@ -117,7 +117,7 @@ void TownsFDC::MakeReady(void)
 		}
 		if(state.lastCmd&0x10)
 		{
-			drv.trackReg=drv.trackPos;
+			SetTrackReg(drv.trackPos);
 		}
 		break;
 	case 0x60: // Step Out
@@ -130,7 +130,7 @@ void TownsFDC::MakeReady(void)
 		}
 		if(state.lastCmd&0x10)
 		{
-			drv.trackReg=drv.trackPos;
+			SetTrackReg(drv.trackPos);
 		}
 		break;
 
@@ -573,13 +573,13 @@ void TownsFDC::MakeReady(void)
 		}
 		break;
 	case TOWNSIO_FDC_TRACK://                0x202, // [2] pp.253
-		state.drive[DriveSelect()].trackReg=data;
+		SetTrackReg(data);
 		break;
 	case TOWNSIO_FDC_SECTOR://               0x204, // [2] pp.253
 		SetSectorReg(data);
 		break;
 	case TOWNSIO_FDC_DATA://                 0x205, // [2] pp.253
-		state.drive[DriveSelect()].dataReg=data;
+		SetDataReg(data);
 		break;
 	case TOWNSIO_FDC_DRIVE_STATUS_CONTROL:// 0x208, // [2] pp.253
 		state.IRQMSK=(0!=(data&1));