z80dma.cpp: add derivateves ZILOG, UA858D, SPEC_NEXT #12658
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sinclair/spec128.cpp: configuration option for DMA extension
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Is there a good way to avoid wedging SpecNext configuration into the base Z80DMA device? (Perhaps UA858D might also be worth supporting as its own type for East German systems such as |
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I was thinking about it too. The problem is that both zx mod and next itself allows switch between two modes. |
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Consider using a virtual sub function that gets overridden in the subclasses? |
src/devices/machine/z80dma.cpp
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| void z80dma_device::do_write() | ||
| { | ||
| if (m_byte_counter && m_dma_mode == dma_mode::SPEC_NEXT) | ||
| { | ||
| m_addressB += PORTB_FIXED ? 0 : PORTB_INC ? 1 : -1; | ||
| } | ||
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| switch(TRANSFER_MODE) |
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I'm confused: why it needs a pre-increment before the transfer occurs?
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You need to look at this in combination with block below. Next mode initialized with exact N transfers value, not N+1 as original z80dma
Not sure it's clear for me. E.g. for Next we have one dma which operates in both modes depending on the port. That means we can init dma in Z80 mode but start in N. |
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Yes, and moving this logic from |
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I can revert specnext_dma files. |
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@ajrhacker @angelosa Better? |
z80dma.cpp: add derivateves ZILOG, UA858D, SPEC_NEXT
sinclair/spec128.cpp: configuration option for DMA extension
details: https://velesoft.speccy.cz/data-gear.htm