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/* Technical */
== Technical ==
Dobbertin HD20 probably uses a modified pc-xt interface which uses is a Winchester type hard disk. The WD1002-SHD datasheet describes a basic set of commands. The status register values are outputs from the chip itself. But here you can find the list of commands, their parameters and results. The other link describes more extensive Winchester commands extending the WD1002. The actual Winchester implementation in the HD20 is not known.
It is claimed it is a PC-XT interface with an interface between that and the CPC.
The OMTI 5510 appears to be very close. The command descriptions and operation appear to be the same although the software seems to only use TEST READY, READ, WRITE, SEEK (parking), SET PARAMETERS and FORMAT.
Uses [[XD-DOS]] v2.10 (which supports the harddisc, and additionally supports external double sided 80 track disc drives). The 20 MB harddisc is split into four partitions, with drive names D, E, F, and G (drive name C isn't used here, but may be used as RAM disc, in combination with Dobbertin RAM expansion). Under [[FutureOS]] the four partitions are named I, J, K and L. The hard disc is controlled by this I/O Ports:
#FBE1 Dobbertin Harddisc Status, Reset
#FBE2 Dobbertin Harddisc Select, Configuration
#FBE3 Dobbertin Harddisc DMA, Interrupt(Used on CPC???)
#FBE4 Dobbertin Harddisc Reset
The hard drive interface is an PC-XT compatible hard disc interface. The CPC's port mappings are close to the PC-XT's port mappings.
To format the hard disk you need to use the CPM based system tools. To use the tools you need to patch a CPM+ disc so that it recognises the hard disk.
The disc format appears to be CPM/AMSDOS based, with 0x0e5 as the format data byte.
== Other harddisc solutions for the CPC ==
