Community Building and Adopting Standards

Sorry for the delay in updates on the NEON Sunrise project. But there’s been a lot of travel in my day job recently and it’s put just about everything on hold.

We’ve been having a pretty good discussion in the Facebook 6502 CPU Family group about building a backplane “standard” for 65xx series SBC. Yes there are some that already exist, the re RC6502 and RC2014, but they’re pin header designs. We want to build an ISA-like card slot interface. The first phases of this are to build a pure backplane with active termination.

Fredric has been working diligently at collecting all our feedback and reimaging it over and over again. After a lot of debate we’ve agreed to use the standard 62 pin connection that the ISA cards did. I’m working on making an extended version to support +/-12V and potentially -5V? Not sure since I am going to carry 12V but not sure who else is.

All this is to say there is no standard for card edge connectors for the 65xxx family of processors, to my knowledge.  I’m not pretentious enough to declare a new standard, but I’m saying that if hobbyists like me want a card edge solution, might as well have a discussion about it.

— Frederic S.

He started with the 98 pin design, but was able to knock it back down to the 62 pin format. He even laid it out so that the +5V (VCC) and GND won’t short a board if it’s put in backwards.

The other big addition to the (it’s not a) standard is active termination in the form of pull-up and pull-down resistors. There is still a lot of debate about which lines to pull high or low and at what values, but as far as laying out a schematic that’s an easy change as the conversation gets finalized. I’m not an electrical engineer, so I’m letting the people who understand it hash it out. I’m already pulling data and address lines low, and and active low lines high in my design. It may mean just putting those resistors at the far end of the slots rather than just near the chips. Which would also help clean things up a bit on the board.

But the main takeaway here is whatever we work out as a community as a pinout for these boards, I will be using in the release version of the NEON Sunrise. Which I’m excited about.