If I remember right, emultating a microdrive completely is probably not a very good idea - The electrical intarface to the drives is typical minimalist Sinclair technology and consists of 3 adress lines to adress the drive (0-7), a motor start line and a read and write line. There's no way to adress a specific sector on a drive, and the technology relies on all sectors of the tape passing the r/w head in a reasonable amount of time - The logic just waits until it "sees" the correct sector header passing by and then starts reading or writing the specific sector. This worked quite well with small capacities of several hundred sectors. I guess nobody wants to wait until all sectors of a 2GB SD have passed the emulated head......
Cheers, Tobias -----Original-Nachricht----- Subject: Re: [Ql-Users] QL SD/MMC-Card interface survey Date: Wed, 12 Jan 2011 21:46:33 +0100 From: Tony Firshman <t...@firshman.co.uk> To: ql-us...@q-v-d.com On 12/01/2011 13:48, Peter wrote: > Tony Firshman wrote: > >> Speaking from pretty little low level knowledge, how about abandoning >> the microdrives completely (I thought you were) > So far, I could have used just one SD card interface, keeping one > microdrive. > > Abandoning the microdrives completely is an option I could think about. > But the task of creating SD card signals is still not trivial. I don't > know exactly how the ZX8302 behaves internally, and which timings are > acceptable. > > For example, the OS even inserts delays when just bit-banging the drive > select daisy chain, and I have no idea why this is required. Line lengths? > Noise? ZX8302 internal requirements? ... Using the ZX8302 for a completely > different purpose might require a lot of time for investigation and > experimentation. > >> and making your interface emulate microdrives? > Hehe, nice idea. Unfortunately it would be a pain in terms of speed, also > size would be limited by the MDV drivers I guess :) > > I bet the drivers could be patched. You could also keep one mdv if the interface was fully compatible. It would be quite hard though switching between the two speeds. I suppose if simultaneous access was barred, the mdv driver could be patched on the fly. As Malcolm suggested, a PIC could be used, and may have enough on board storage to buffer one boot image. Failing that it could be a bootstrap to load from the card. Laurence Reeves knows a *lot* about the logic. Tony _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
