R/W line is also derived onto expansion port and it's 'pull-up' so it can be driven by any device (not only by CPU or Video Controller =VIC). Second thing is used for implementation of DMA transfer in which DMA input is set to '0'. You may say that C64 has already implement logic for DMA type of data transfer.įirst characteristic of C64 is used to 'plug in' control registers of FDD in address space of C64 making possible to read/write control/status bits from FDD controller by simplest BASIC instructions such as PEEK or POKE. C64 has DMA input making possible to stop operation of CPU and to take full control over data and address bus.This address space in C64 is decoded by two signals (I/O1 and I/O2 ) which are derived on the expansion port of C64 C64 has 512 bytes of address space reserved for I/O devices similar to the PC I/O address space of 1024 bytes in which you can find control register of serial,parallel ports and other I/O devices within PC.Two advanced features of C64 (almost unknown to the most users of C64) were very helpful in constructing DDemon: Advanced characteristic of C64 and problems
This characteristic makes possible to transfer files from C64 to PC (and vice versa) without any software conversion. With this (programmed in C64 assembler) you have ability to read and write to 1.44Mb diskette in format which is compatible whit DOS/Windows operating system on PC (files from C64 are readable on PC).
Īlso I have developed a system software for controlling FDD whit ability to emulate PC-DOS system on C64 (shell as Norton Commander) which makes possible that a files from C64 can be recognized on PC and vice versa. Because of that I have applied a DMA (Direct memory access) type of data transfer which demands additional electrical circuits. C64 computer is too slow for working with FDD which uses data transfer rate of 500Kb/sec. I have used standard floppy diskette drive (FDD) which uses a standard 1.44Mb diskettes. I will describe one of the hardest way for connecting PC and C64: Electric scheme of interface between C64 and ISA card (picture from Electronic Work Bench).List of hardware and software that you need.Advanced characteristic of C64 and problems with construction of DDemon.How to connect PC 1.44Mb floppy-diskette drive to oldie C64 - DDemon project
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