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Added support for including the loader binary in the .cdt file. #2

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Added support for including the loader binary in the .cdt file. #2

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bf63edd
Added support for including the loader binary in the .cdt file.
smeg-of-lister Aug 22, 2021
b0a43e6
Fixed a couple of errors in the comments..
smeg-of-lister Aug 22, 2021
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118 changes: 111 additions & 7 deletions GenerateCDT/GenerateCDT.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,8 @@


def main():
if (len(sys.argv) != 4):
print "Usage: %s datafile outfile zero_duration" % sys.argv[0]
if (len(sys.argv) != 4 and len(sys.argv) != 5):
print "Usage: %s datafile outfile zero_duration [loaderfile]" % sys.argv[0]
return

zeroBitLength = int(sys.argv[3])
Expand All @@ -18,10 +18,24 @@ def main():
oneBitLengthLow = oneBitLength & 0xFF
oneBitLengthHigh = (oneBitLength >> 8) & 0xFF


if len(sys.argv) == 5:
loaderFileName = sys.argv[4]
with open(loaderFileName, mode='rb') as fin:
loaderContent = bytearray(fin.read())
fin.close()
loaderLength = len(loaderContent)
loaderLengthLow = loaderLength & 0xFF
loaderLengthHigh = (loaderLength >> 8) & 0xFF
loaderSegments = loaderLength // 256 + 1 # Calculate number of 256 byte segments required
loaderBlockLength = loaderSegments * 258 +5 # Caclulate block length (data + flags + checksums + trailer)
for i in range(loaderSegments * 256 - loaderLength): # Pad loader up to the next 256 byte boundary with zeroes
loaderContent.append(0x00)
loaderBlockLengthLow = loaderBlockLength & 0xFF
loaderBlockLengthHigh = (loaderBlockLength >> 8) & 0xFF

dataFileName = sys.argv[1]
with open(dataFileName, mode='rb') as fin:
fileContent = fin.read()
fileContent = bytearray(fin.read())
fin.close()
contentLength = len(fileContent)
contentLengthLow = contentLength & 0xFF
Expand All @@ -30,7 +44,97 @@ def main():
data = bytearray('ZXTape!')
data.append(0x1A)
# Version
data.extend([0x01, 0x0D])
data.extend([0x01, 0x14])

# Standard CPC header block
# TZX header
if len(sys.argv) == 5:
data.append(0x11) # Block ID
data.append(0x21) # Pilot pulse length (L)
data.append(0x0B) # Pilot pulse length (H)
data.append(0xAD) # Sync1 pulse length (L)
data.append(0x05) # Sync1 pulse length (H)
data.append(0xAD) # Sync2 pulse length (L)
data.append(0x05) # Sync2 pulse length (H)
data.append(0xA2) # Zero pulse length (L)
data.append(0x05) # Zero pulse length (H)
data.append(0x05) # One pulse length (L)
data.append(0x0B) # One pulse length (H)
data.append(0x02) # Pilot pulse count (L)
data.append(0x10) # Pilot pulse count (H)
data.append(0x08) # Bits used in last byte
data.append(0x11) # Pause after this block (L)
data.append(0x00) # Pause after this block (H)
data.append(0x07) # Data length (L)
data.append(0x01) # Data length (M)
data.append(0x00) # Data length (H)
# CPC header
data.append(0x2c) # Flag (0x2c for header, 0x16 for data)
data.extend([0x48, 0x59, 0x50, 0x45,\
0x52, 0x4C, 0x4F, 0x41,\
0x44, 0x45, 0x52, 0x00,\
0x00, 0x00, 0x00, 0x00]) # Filename ("HYPERLOADER" padded to 16 bytes with zeroes)
data.append(0x01) # Block number
data.append(0xFF) # Last block indicator (non-zero = last block)
data.append(0x02) # File type
# Bits 1-3 determine file type:-
# 0 BASIC
# 1 Binary
# 2 Screen Image
# 3 ASCII
# 4-7 Unused
data.append(loaderLengthLow) # Data length (L)
data.append(loaderLengthHigh) # Data length (H)
data.append(0x00) # Destination address (L)
data.append(0x40) # Destination address (H)
data.append(0xFF) # First block indicator (non-zero = first block)
data.append(loaderLengthLow) # File length (L)
data.append(loaderLengthHigh) # File length (H)
data.append(0x00) # Exec address (L)
data.append(0x40) # Exec address (H)
for i in range(228):
data.append(0x00) # Pad up to 256 bytes with zeroes
data.append(0xD2) # Checksum (H)
data.append(0x00) # Checksum (L)
data.extend([0xFF, 0xFF, 0xFF, 0xFF]) # Trailer

# Standard CPC data block
# TZX Header
data.append(0x11) # Block ID
data.append(0x21) # Pilot pulse length (L)
data.append(0x0B) # Pilot pulse length (H)
data.append(0xA6) # Sync1 pulse length (L)
data.append(0x05) # Sync1 pulse length (H)
data.append(0xA6) # Sync2 pulse length (L)
data.append(0x05) # Sync2 pulse length (H)
data.append(0x8B) # Zero pulse length (L)
data.append(0x05) # Zero pulse length (H)
data.append(0x1D) # One pulse length (L)
data.append(0x0B) # One pulse length (H)
data.append(0x02) # Pilot pulse count (L)
data.append(0x10) # Pilot pulse count (H)
data.append(0x08) # Bits used in last byte
data.append(0x78) # Pause after this block (L)
data.append(0x11) # Pause after this block (H)
data.append(loaderBlockLengthLow) # Data length (L)
data.append(loaderBlockLengthHigh) # Data length (M)
data.append(0x00) # Data length (H)
# CPC Data
data.append(0x16) # Flag
for i in range(loaderSegments):
crc = 0xFFFF # CRC initial seed
for j in range(256):
data.append(loaderContent[j]) # Add byte from loader
k = crc >> 8 ^ loaderContent[j] # CRC iteration
k = k ^ k >> 4
crc = crc << 8 ^ k << 12 ^ k << 5 ^ k
crc = crc & 0xFFFF
crc = crc ^ 0xFFFF # One's complement for final CRC value
crcHigh = crc >> 8 & 0xFF
crcLow = crc & 0xFF
data.append(crcHigh) # Checksum (H)
data.append(crcLow) # Checksum (L)
data.extend([0xFF, 0xFF, 0xFF, 0xFF]) # Trailer

# Block group
data.append(0x21) # Block ID
Expand All @@ -40,8 +144,8 @@ def main():
data.append(0x12) # Block ID
data.append(0x22) # Pulse length (L)
data.append(0x0B) # Pulse length (H)
data.append(0xFF) # Pulse count (L)
data.append(0x03) # Pulse count (H)
data.append(0x00) # Pulse count (L)
data.append(0x04) # Pulse count (H)
Comment on lines +147 to +148
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@smeg-of-lister smeg-of-lister Aug 22, 2021 •
edited
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I incremented the pulse count here because the emulator I'm using (RetroVirtualMachine) doesn't seem to implement ID12 blocks with an odd number of pulses correctly for some reason (either that or it's not setting the signal level correctly somewhere). This change doesn't seem to affect loading on real hardware.


# Pure tone 2
data.append(0x12) # Block ID
Expand Down