Hello Ruud,
>> needs either ECP
>I never have thought about using this for DMA :( What does one need to be
>able to use it for DMA-ing with a C64?
ECP seems to be a fairly complicated mode and the speed improvement is not
that much higher than the EPP mode.
The EPP mode automates the hand shaking lines and the receiver can easily
meet the specification using simple TTL and a few delays (even the the 8255
comes close). There are two "buffers" one 1byte (address) and the other
4bytes (4x 8bit data). Hence you can send 4 8bit bytes per I/O write.
The ECP uses similar signal timings, but the problem is where the device
must request service from the PC. The DMA mode allows a section of PC RAM to
be configured as "send this to the device", and after this there is no
further need to control the I/O card. I've been told though that like PCI,
the device needs a special LSI in order to handle it.
That's about the extent of my knowledge - perhaps someone knows more. It
seems a very interesting way to do things, if it wasn't for needing the
LSI...
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