GARTHWILSON wrote:
Daryl's 65SPI IC shifts a byte in and one out (SPI goes both directions simultaneously) in 16 clocks. You'll probably need that much time just to handle each byte during the process anyway; so it wouldn't be slowing you down. He is re-working the design for a newer CPLD since the old one became unavailable. I still have several here I could let go of. The 6522 has a synchronous serial port that's just as fast, although not bidirectional. A few people have used it for one of the SPI modes. I'd have to sharpen my pencil to see what tricks (if any) there might be to using it for SPI.
You read my mind, I was just trying to find a source for the chips like this, although I saw the SPI65b which seemed interesting as well, but I would be interested in chips to get me going on SPI with something that's simple and clean (I can bit bang if necessary, but I'd prefer to offload it from the CPU)
GARTHWILSON wrote:
The monochrome graphics LCD I've used, and another I plan to use, take a command to tell which dot row and column to start with in its internal memory. In this one, it wraps IIRC, so you would have to re-draw just the one row or column that wrapped around to the other side or end. I know I've seen other ones though that have an internal memory that's larger than the screen, so there's a certain amount of panning you can do without re-drawing anything.
this is interesting, and I've been revisiting the displays section, with a text display in mind for the original build (I'd like to do one big enough to run a BASIC interpreter without killing myself moving lines up and down on a 2 row screen)
GARTHWILSON wrote:
Yes, just change the bytes you want to, and take advantage of the rest already being what you want.
This is kind of what I wanted to do with the original "like a GIF" idea, but as was pointed out earlier, there's a SRAM IC that does composite video out, and small displays compatible with composite, so when I get to color video, I'll probably take that route, to take the heavy lifting off the 6502
GARTHWILSON wrote:
You can often get free dual-trace, triggered CRT oscilloscopes that businesses or schools are getting rid of, in the range of 20-100MHz. Do yourself a favor and get a decent scope. One of these will be way better than most of the cheap new digital ones like the worthless DSO Nano you hook to your computer, and certainly better than the scope from the 1950's. Just be sure to get a decent pair of 10x probes with it, and take care of them. Good probes are not cheap. There's a lot more there than meets the eye. (The 6502 primer's
section on basic workbench equipment discusses this.)
Ya, the 1950s one is neat to use to look at audio, and watch the vacuum tubs work, but not much else, it's also a huge fire hazard because it's a caseless design with a ratsnest underneath instead of a board
GARTHWILSON wrote:
You're welcome. It was written to answer a lot of questions and problems that kept coming up over and over in the early years of the forum. It does get frequent small updates. The whole site probably has a thousand links, and I definitely can't check them all every week; so if you find that one has gone dead, please let me know.
I actually did find some dead links, I'll try and go through and document them for you soon, a bit busy at work atm though
GARTHWILSON wrote:
It's mostly unrelated. If anything, a lower voltage may cause less trouble, because parts are the fastest at their maximum voltage, producing faster edge rates that are more likely to cause ringing and double triggering, and also responding more quickly to it and being less forgiving.
I suppose it will mostly be based on what my critical ICs run at, so I'm not having to level shift between them and the CPU, I'd like to have the option to clock faster in the future though, in case my board is capable
GARTHWILSON wrote:
There are of course thru-hole sockets for PLCCs. Remember also that if you need additional parts or connections on the other side from a DIP, you can forgo the holes and just put pads down on the board to solder the DIP to, holding it on with solder fillets. That should be fairly easy to unsolder too, using solder wick.
As far as PLCCs go, and other programmable chips, I've never used them, and I'm not sure how to use them, I'm willing to learn though, as it seems a lot of ICs are not really made with the 6502 in mind, so I may need to implement some custom functionality. As far as the connections go, I'd prefer to have sockets and cleanly solder everything if possible, although I'm not sure how long a trace length is "too long" for different clocks
This picture shows a board I made up for 2 IO expanders, (I set up the addressing wrong on it) it is 2 sided, and you can see some of the traces on the top, this I generally how I like to set it up, except with sockets (this board was an early test)
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