Method DecodeLatchNibble

source/DiskFormatTrack.cpp:223–325

}

void FormatTrack::DecodeLatchNibble(BYTE floppylatch, bool bIsWrite, bool bIsSyncFF)
{
	m_uLast3Bytes <<= 8;
	m_uLast3Bytes |= floppylatch;
	m_uLast3Bytes &= 0xFFFFFF;

	if (m_trackState == TS_GAP2_START && bIsWrite)	// NB. bIsWrite, as there's a read between writing Addr Field & Gap2
		m_trackState = TS_GAP2;

#if LOG_DISK_NIBBLES_WRITE_TRACK_GAPS
	if (bIsSyncFF && (m_trackState == TS_GAP1 || m_trackState == TS_GAP2 || m_trackState == TS_GAP3))
	{
		if (m_bmWrittenSectorAddrFields == 0x0000 && m_trackState == TS_GAP1)
			m_DbgGap1Size++;
		else if (m_bmWrittenSectorAddrFields == 0x0001 && m_trackState == TS_GAP2)
			m_DbgGap2Size++;	// Only count Gap2 after sector0 Addr Field (assume other inter-sectors gap2's have same count)
		else if (m_bmWrittenSectorAddrFields == 0x0001 && m_trackState == TS_GAP3)
			m_DbgGap3Size++;	// Only count Gap3 between sector0 & 1 (assume other inter-sectors gap3's have same count)
		return;
	}
#endif

	// Beneath Apple ProDOS 3-14: NB. $D5 and $AA are reserved (never written as data)
	const UINT32 kADDR_PROLOGUE_DOS3_3 = 0xD5AA96;	// D5AA96 is used by DOS3.3/ProDOS
	const UINT32 kADDR_PROLOGUE_DOS3_2 = 0xD5AAB5;	// D5AAB5 is used by DOS3.2/3.2.1
	if (m_uLast3Bytes == kADDR_PROLOGUE_DOS3_3 || m_uLast3Bytes == kADDR_PROLOGUE_DOS3_2)
	{
		m_bAddressPrologueIsDOS3_2 = (m_uLast3Bytes == kADDR_PROLOGUE_DOS3_2);
		m_trackState = TS_ADDRFIELD;
		m_4and4idx = 0;
		return;
	}

	// NB. If TS_ADDRFIELD && m_4and4idx == 8, then writing Address Field's epilogue
	if (m_trackState == TS_ADDRFIELD && m_4and4idx < 8)
	{
		m_VolTrkSecChk4and4[m_4and4idx++] = floppylatch;

		if (m_4and4idx == 8)
		{
			for (UINT i=0; i<4; i++)
				m_VolTrkSecChk[i] = ((m_VolTrkSecChk4and4[i*2] & 0x55) << 1) | (m_VolTrkSecChk4and4[i*2+1] & 0x55);

#if LOG_DISK_NIBBLES_READ
			const bool chk = (m_VolTrkSecChk[0] ^ m_VolTrkSecChk[1] ^ m_VolTrkSecChk[2] ^ m_VolTrkSecChk[3]) == 0;
			if (!bIsWrite)
			{
				BYTE addrPrologue = m_bAddressPrologueIsDOS3_2 ? (BYTE)kADDR_PROLOGUE_DOS3_2 : (BYTE)kADDR_PROLOGUE_DOS3_3;
				m_strReadD5AAxxDetected = StrFormat("read D5AA%02X detected - Vol:%02X Trk:%02X Sec:%02X Chk:%02X %s",
					addrPrologue, m_VolTrkSecChk[0], m_VolTrkSecChk[1], m_VolTrkSecChk[2], m_VolTrkSecChk[3], chk?"":"(bad)");
				if (!m_bSuppressReadD5AAxxDetected)
				{
					LOG_DISK("%s\r\n", m_strReadD5AAxxDetected.c_str());
				}
			}
#endif
#if LOG_DISK_NIBBLES_WRITE
			if (bIsWrite)