Hei, On Tue, Apr 26, 2011 at 09:04:07PM +0200, Spiro Trikaliotis wrote: > The problems are different when using the PC as a IEC controller > (connecting a 154x TO a PC) instead when using the PC as floppy drive. > > In both cases, there is the problem with the "listener hold off" (cf. > http://www.trikaliotis.net/opencbm#faq_hw, second question). This one is > solved with the "multitask cable(s)" XM1541 and XA1541. > > OTOH, a IEC drive must react to an activated ATN within 1ms, or the > controller (the C64, C128, or whatever) will miss that it is connected. > 1ms seems like a long time; unfortunately, with a multitasking OS, it > can be tricky to achieve this. That's why a DOS only solution is much > easier here: You have control about the exact timing. I am wondering if it's possible to use ATN line then to generate an IRQ on the PC side (so you don't need polling). This means the need to write a custom driver then of course, but maybe it can be done then using a more modern OS (I am thinking about Linux, anyway I wouldn't try to write a device driver for Windows ...). However I am still not sure, it can be garantueed even with IRQ on the PC side to have that 1ms, and since I don't know deeper thing on IEC protocol, I am sure it's not just this simple as I imagine ... (I only know that damn IEC ATN wire, I can't solder to the DTV board only at the n'th time ....). Honestly, since the need of parallel port, MSDOS, etc, I think the way should be followed to use some kind of uC at least, which is a much "comfortable" solution and no need to have "extra" stuffs like a PC running DOS ... I know about projects like 1541-III, SD2IEC and such. However, I still think I don't want to "fight" with memory cards etc, when my goal is to use PC "as the drive" but in a modern way, let's say via USB connection. Is there any project like this? As far as I can see, the mentioned projects by me are mainly focused on various memory cards (or connecting a real 1541 to PC again, just with USB), while I would like to use my PC as the data source (of course it's acceptable to transfer at least some parts of - let's say - the disk image to the uC, just I don't want to write/read memory card on PC, change it, read/write with the CBM machine on the end of an 1541-III or so, change it, etc etc ...). Some cross-development projects would need this for me, that I can easily access data from both of C64 and PC but using no special software on the C64 (or DTV) side. For this, I think the best solution is to use the PC as the 1541 itself, that's the reason of my whole thread here. > > BTW, the 1541EMU uses another trick: It helps with hardware, using the > same "ATN trap" as present on an original 154x, 157x or 1581, using an > XOR gate. This way, the floppy drives reacts almost instantly to the > ATN, and the PC/the floppy can take as much time as needed in order to > react on it. > > (Yes, even the 1541 can have problems reacting in 1ms to the ATN. This > is the case whenever the floppy has a long task to do in the interrupt, > for example, when formatting a disk.) > > I hope this clarifies things a little bit. yes, thanks for the information - Gábor Message was sent through the cbm-hackers mailing listReceived on 2011-04-26 21:00:13
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