Delivery Day!
My Jameco (#NotSponsored) package arrived a day early, and my work can continue on the 6502.
Most of the shipment is for either the serial port, or the real time clock, the current and next projects.
10 @ 74LS32 Dual 4-Input AND gate
10 @ 74LS20 Dual 4-Input NAND gate (oops, but I'll keep them around)
10 @ 7432 Quad 2-Input OR gate (unfortunately LS series wasn't available)
5 @ MAX232 Line Drivers
25 @ 330Ohm Resistor Nets
2 @ 28 pin ZIF Sockets, which are much higher quality than the green one I have.
3 @ 9 pin D-Sub connectors
5 @ CR2032 Batteries and Holders
1 @ Dallas DS1511Y Real Time Clock
5 @ 1.8432MHz Crystals
3 @ 3.6864MHz Crystals
So the 7400 series chips are obvious, I'm building logic gates for the memory map. Albeit, I ordered the 74LS20s by accident, thinking I needed NAND gates when I needed AND gates, but left it in the order anyway. It'll find a use someday, I'm sure.
The resistor nets are in case I want to break out LEDs again, which I will do at some point. Also might be useful in the VGA circuit someday.
The line drivers, the crystals and the D-Sub connectors are for the serial connection. I'm thinking with the 3.6864MHz I can set the default speed at 38.4 Kbps instead of 19.2 Kbps? Not sure if that's even necessary, but I'll play with it. I figure if that's going to be the main connection to the outside world... until we make an 8-bit Ethernet card 👀, which isn't as crazy as it sounds since someone has made one for the Apple ][.
In other news...
I took the clock circuit design that I'm currently using on the v0.2 mainboard, and incorporated it into a drop in idea that would fill the footprint of a Full Can Oscillator. It's the same circuit, but with the enlarged footprints for the resistors and the polarized capacitor at C4 inserted and oriented so I don't have to spend time worrying about that again.
I did reduce the LED from a 5mm to a 3mm, and upped the current limiting resistor from 330 to 390 Ohm to dim it a bit since it's not intended to be the focal point of the board. The other major convenience design update is the 1M Pot now accepts either inline pins or offset pins, with the two centers being tied to each other and to ground.
I did it all with only one via, and could have gotten that to zero if I really wanted to, but I didn't want to round one line all the way around the board for no good reason.
If there is interest, I'd be willing to redesign this again and do all surface mount parts, including the 555 chip to get the footprint all the down to just the size of the can as a true drop in replacement. I think I can manage that, but I won't bother unless it looks like something people might want. I did order 10 of these boards (it was the same price as 5 because they're so small), and should have them early next week.