DC2N by Luigi Di Fraia DC2N - a tape preservation device for Commodore and Sinclair homecomputers


Description Media files Ordering PC Software FAQ
DC2N navigation pane by Luigi Di Fraia
This page has last been updated on: 27 Mar 2014.


DC2N DMP format specification (version 0):

Offset Size Description
0x00 12 bytes ID string: "DC2N-TAP-RAW"
0x0C 1 byte Format version: 0
0x0D 1 byte Machine for which the tape content is intended
  • 0 = Commodore 64
  • 1 = VIC 20
  • 2 = Commodore 16, Plus/4
This information is only used to convert to TAP format.
0x0E 1 byte Video standard for which the tape content is intended
  • 0 = PAL
  • 1 = NTSC
This information is only used to convert to TAP format
0x0F 1 byte Counter resolution [bit]: 16 in DC2N
0x10 4 bytes Counter rate (LSBF) [Hz]: 2000000 in DC2N (0x80 0x84 0x1E 0x00)
0x14 any 16-bit (i.e. counter resolution) data values (LSBF). Each byte is MSbF.

The DC2N format is used for RECORD/dump operations respectively. The DC2N DMP file resolution (2 MHz) is more than 16 times the one used by the legacy TAP format (123.156 kHz).

Each data value is the delay, expressed in clock cycles (at Counter rate), between two consecutive rising (falling) edges of the Commodore computer write line (C2N read line) signal.
0xFFFF is an overflow value, meaning that the next data values should be summed to this one to build up the total delay, up to the first non-0xFFFF value (included). Anyway, we don't really require to deal with that since the dc2nconv software converts DC2N 16-bit files to legacy TAP v1 files, which are already supported by many emulators and tools.


DC2N DMP format specification (version 1 - BETA):

Offset Size Description
0x00 12 bytes ID string: "DC2N-TAP-RAW"
0x0C 1 byte Format version: 1
0x0D 1 byte Lower 4 bits: Machine for which the tape content is intended
  • 0 = Commodore 64
  • 1 = VIC 20
  • 2 = Commodore 16, Plus/4
Upper 4 bits: Type of event used to define pulse start/end
  • bit 4: 0 = dump (starts at falling edge), 1 = record (starts at rising edge)
  • bit 5: 0 = measure length of 0+1 states as a whole, 1 = measure length of 0 and 1 states individually
This information is only used to convert to TAP format.
0x0E 1 byte Video standard for which the tape content is intended
  • 0 = PAL
  • 1 = NTSC
This information is only used to convert to TAP format
0x0F 1 byte Counter resolution [bit]: 16 in DC2N
0x10 4 bytes Counter rate (LSBF) [Hz]: 2000000 in DC2N (0x80 0x84 0x1E 0x00)
0x14 any 16-bit (i.e. counter resolution) data values (LSBF). Each byte is MSbF.

Although DMP version 1 with all 4 event bits clear is equivalent to DMP version 0 (for dumped files only), the latter is preferred due to the number of DMP version 0 files already available at this stage.
DMP version 1 is recommended only for those cases where recording the 0-state and 1-state of square waves is necessary (e.g. for C16 where the MCU is capable of detecting such states individually and a few turbo loaders take advantage of that - such as the turbo loaders used by freezers).

Anybody can support the DMP format in their own software, as long as the following conditions are met:
  • DMP files must only be written using a hard real-time system used for doing the sampling
     
  • DMP files must NOT be edited: that includes trimming, splitting, enhancing, or correcting them (only exception being manual changes required to restore corrupted data: when that happens, both the original and restored DMP files together with a detailed report of the changes have to be bundled together and made available at the same time, i.e. not just "upon request")
     
  • DMP files can be used for waveform generation, both in hardware or software
     
  • DMP files can be converted to TAP format (preferably version 1 or later)
     


Power supply:

DC2N is a digital device so that it needs a regulated power supply while dumping tapes. The required voltage is 5V DC. Power supply units that erogate 800mA, 1A, and 2A have been tested without issues so far.

In some countries it is easier to get a 4.5V DC PSU. That's been tested with different results: some PSUs are unable to erogate the required current, therefore the tape drive motor is slower than it should be and pulses have a longer duration than their nominal values. To be on the safe side, avoid anything that's not a 5V PSU.

2.5mm (inner)/5.5mm (outer) DC plugs fit into revision 2.0. The inner part has to be 5V, the outer one GND.

DC plug to be used in conjunction with the DC2N deivce by Luigi Di Fraia

Polarity of the DC plug to be used in conjunction with the DC2N device by Luigi Di Fraia



Serial terminal settings (optional):
  • baud rate: 57600
  • data bits: 8
  • parity: none
  • stop bits: 1
  • flow control: none
A terminal program can be useful to monitor data while dumping, as shown here.

The connection to a PC'serial port is made using a Serial RS232 9 pin Male to Female cable, NOT a null-modem one.

Serial RS232 9 pin Male to Female cable to be used in conjunction with the DC2N device by Luigi Di Fraia

One end of the lead has to be MALE (it fits into the DC2N) and the other one has to be FEMALE (it fits into the PC serial port).


Comers since area creation: Since April 2002 - Best viewed at 1024x768



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