Status update so far ..
So all the main wiring is in; its toggling between pages very nicely and solidly (for 1x600 mode anyway, since I'm still doing it all in C code until the wiring is proven.)
I set up a clear-to-blue (or white, black, whatever) routine on the cpu, having it run every time the bank switches, and setting the swithcing to occur say every 30s instead of on VBLank, so I can have an easier time seeing whats going on.
Bank-2 seems to clear fully blue (awesome, success!)
Bank-1 seems to clear mostly blue (poop :/)
Problems:
- the shark-fin type SMD adaptor board I'm using isn't seating well; I mean, it just comes with two rows of holes, so I put in right-angle headers; headers long enough to do it aren't very common, so I've had to stretch and wrestle a bit, and in the end.. getting the spacing just-so didn't work out perfectly.. so this thing standing up seems not to get contacts in for address-lines sometimes; if I rock it back and forth, it seems to shudder and funk out depending which way I touch it. (Mind you, since theres only one set of address lines, and they're switcvhing back and forth between two banks, and one bank clears right.. it stands to reason that the cpu is wired up right.. no?)
- 9V battery .. I'm using a 7805, so its spitting out 5V; but these things need about 7+V so it can down to 5V at all; a 9V battery, being used here, will drop to about 7V after only an hour or two of runtime (I've not measured current draw here at all recently.. but must be significant..); so I don't leave it going all the time, just when flashing or running it, but still. uses up 9V 'enough' fast; I'm sure these batteries could run other stuff just fine for many more hous, but my board requires a good 7.5V+ or so..
Guess I should wire into my power supply mini-board a 9V wall wort adaptor... keep it running on mains indefinately; I've been lazy, but I think I bought the socket and wall wort already, just need to connect it
The o-scope is showing its value here (again); its had to get a probe in through this dense forest of wires, but I can at least see which address lines and I/O lines are active and when; ie: as the banks switch, one chip should go fairly quiet on the I/O lines and many of the address lines.
ie: cpu facing ram bank - I'm doing full 16bit blanking, so every I/O and address line should be hit
gpu-facing ram bank -- its address lines from 1-600 are being set, with I/O going to DAC->VGA; so bottom 10 address lines should be busy (perhaps I should rig it to slide up through the top bits as well, so I can test all address lines there too..)
It'll take awhile, but the goal here is to find out.. where the problem is; is it cpu seating issue (Doesn't _Sound_ like it, but I know it does loosen up 10% of the times.. so its a problem across the board now; just blinking a LED is always solid, but other operations are flaky.. but that'll go away if I solder things down; or maybe I need to pop out the sharkfin, and solder right to a perfboard, and then jumper over to the breadboard, or something.. just to make it solid. (Actually, I have male/female jumper wires, maybe I should just jumper it over nice and floppy, but that sounds like another disaster waiting.. can't move anythign without that popping out, and I like to tilt it to look at connections and probe, etc.)
- or is it the I/O or address lines to one bank or the other; seems like one bank is the naughty one (at least in the 1-600 address lines), so sounds like a low-10 address problem to me.
.... if so, could be a MUX isn't hooked up right or loose, or jumper to/from MUX or to/from RAM is funky; thats still about what, 30 wires to chekc, and on a BB its very hard to tell.. but doable
So need a half day to probe this all to hell with the o-scope
Still, the basic design _is working_, just fighting breadboard wrinkles here!
jeff
I suppose.. given one bank works perfect, and the other is got holes;; I could write a single-bank boucning-bar demo or something, should work fine. But I really want both banks to work, damnit, as that is the point of all this
If I just wanted a single bank system, I coudl toss what, 80% of these chips out