Started by doragasu, 00:33, 15 January 17
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Quote from: doragasuAfter a long hiatus, I am resuming this project. I got the PCB fabricated and assembled a prototype. Plugged it to a CPC, and after a bit of debugging, I got basic ROM switch function almost working. And I say almost because ROMs apparently get properly enumerated (the ones printing messages on screen, print them as intended), but once the "READY" prompt appears, the CPC freezes: there is no response to keypresses... I would appreciate help to debug this thing, because I am currently out of ideas.Also while debugging this, I have noticed something that looks strange. If I unplug the CPC and test continuity between #EXP (pin 48) and GND, I find there is a short. In the schematic I have, this pin is only connected to the PIO and to a 2k2 pull-up, so I suppose I should not see this short! I have 2 CPCs, and this is happening in both of them, so if the PIO has been damaged (presubably because of the ROMBA), it has happened in both of them. So is my PIO broken, or am I missing something? Can anyone please check if there is a short between pin 48 of the expansion port and GND.
Quote from: gerald on 17:33, 13 March 18And on a 6128, if you open the link, your cpc will try to boot from a CPM floppy. No more basic
Quote from: GUNHED on 01:29, 19 April 18Quite nice! And everybody else always told me that DMA wouldn't be possible on CPC.
Quote from: Bryce on 09:44, 19 April 18And everybody else was correct. The "DMA" that Doragasu is showing isn't true DMA, because the CPU is being halted while the transfers are happening. In true DMA the CPU would continue to execute commands while the RAM is being accessed by others.But I'm still impressed with this project, very cool indeed.Bryce.
Quote from: tjohnson on 09:53, 20 April 18I don't really understand what I'm looking at, the logo moves stops then the sound plays then the screen changes and wobbles, is the dma taking place to transfer the sound while the logo is moving?
Quote from: Munchausen on 01:40, 19 April 18I wonder about the potential for it to operate along side the M4, perhaps they can be mapped separately?
Quote from: doragasu on 20:04, 22 April 18@Munchausen About moving sprites, basically it is what you have already written: for this to be useful, the DMA engine needs to be aware of the screen layout, to be able to copy "square/rectangle" rom regions. You can program transfers for each line, but as starting a DMA transfer requires 6 writes to I/O region... Also for moving sprites, the DMA engine should have some masking capabilities (e.g. if the pixel colour is 0xF, skip write). I could implement these features on a bigger CPLD/FPGA, but I would not like to increase the cost of the cartridge.
Quote from: doragasuI do not know about M4 internals, but unfortunately I don't think they can "cooperate" (e.g. use DMA to transfer data from M4 memory to internal CPC RAM) because current implementation only allows reading from the ROM embedded inside the cartridge.
Quote from: Munchausen on 00:58, 23 April 18I was thinking more that if you could have both connected at the same time, it would be possible to download things using the M4 and copy them into your DMA ROM expansion. But the M4 already maps 16 ROMs, so is it possible to perhaps map your expansion to roms 17-32?
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