Current events
Administratrivia
A few notices. You may have already seen that the wiki and WebSVN have been unavailable pretty frequently recently. This is because the server this all runs on is dying of a suspected case of Capacitor Plague. Unfortunately, I don't have physical access to the machine.
So in the meantime, I've moved the site onto a computer at home. This means things may run a bit slow - firstly, it's having to share the pathetic 256K upstream you get with ADSL with all my other network traffic, and secondly, it's now practically running on a retrocomputer - the only spare hardware I have with sufficient memory is an old 333MHz UltraSPARC system (I don't want to run it on my PC, for one, I the fan in the new PSU on my PC is so loud I can hear it in the next room, which happens to be where I sleep). It could have been a lot worse, it could have ended up on the old VAX that I have, then you'd have had to have waited about 5 minutes for a page load!
The SVN repo isn't yet back up, but it will be shortly, so you may find some broken links in the wiki.
Winston 00:11, 14 January 2009 (UTC)
Through port success
As I said last time, the NMI problem turned out to be a software bug. Gasman kindly let me use the Open ZX ROM keyboard routines under the MIT license from his GPLd OpenZX ROM project which saved me the effort of writing and debugging one. I wanted to use someone else's as it's likely to have already been debugged, and I need to start getting some of the prototypes out soon.
So the board now works great with the ZX-CF plugged into the back of it, including the Spectranet NMI menu, so now my +3 has both access to a CF card and the network. I tested all the prototypes by loading the new ROM image off the CF card and programming them that way. This meant I had to cut slots in the through ports of all the PCBs, but the job's now done. (I only found out later that PCB Cart would cut the slots for me if I included them in the PCB outline).
I think the combination of a ResiDOS device and the Spectranet could lead to some very good things.
Winston 19:46, 3 January 2009 (UTC)
Through port testing
Happy new year!
The first job of 2009 is to test the through port. The last time I did any testing was on the prototype-for-the-prototype (the breadboarded monstrosity that eventually got turned into the prototype PCB), with the DivIDE. Since then, I have got a ZX-CF board, which has ResiDOS, and as such is a bit more complex than the DivIDE.
So I had to cut a slot in a prototype PCB (something I need to do for the rest of the boards I've made). The DivIDE works pretty much perfectly, The ZX-CF is a little more awkward. It generally works fine, but its execution trap method seems to be very aggressive and it still traps NMI even when the Spectranet traps it...no, update, scratch that -- it's actually a bug in the NMI handler. Well, not a bug as such, but after looking at the logic in the CPLD and scratching my head a bit, I remembered that to save memory in ROM page 0, I had used the ZX ROM's keyboard handler...this of course, means a call out to the Spectrum ROM, and the return comes back in via RST 8. Oops. In light of this, I probably ought to put a key scanning routine into one of the Spectranet ROM pages so it's not necessary to call the ZX ROM. I ought to do that before tinkering with TNFS any more!
I already expected the RST 8 trap on the Spectranet to need disabling, with ResiDOS running - only one board should be allowed to handle RST 8. But none of these are fatal problems. The Spectranet socket library can still be called with the ZX-CF plugged into the back of the Spectranet, due to the unique design of the library entry point instruction trapping. I tested this with the IRC client - I put Spectrum IRC onto a CF card, and loaded it with ResiDOS, then connected to IRC. All this means is with the ZX-CF at least, utility programs should be stored on the CF card and loaded with ResiDOS, rather than using the Spectranet NMI button. (It should be perfectly possible to write network aware ResiDOS modules, too).
The RESET trap works fine too, with the ZX-CF, because that's pre-triggered by the reset signal itself, and as such A15 is already being held high when the CPU begins executing instructions.
Winston 17:03, 1 January 2009 (UTC)