I recommend you lose the filled planes (aka ground pours). All those are doing for you is adding unwanted parasitic capacitance. This is something I've been wondering about but haven't done enough research on. I was under the impression that it wouldn't be any different, essentially, than the ...

So I realized that I can try to use the place where the ROM socket was going to be to connect to the address bus (minus the top bit), and the data bus; basically, all but a small handful of the required signals are available via through-holes. So, I'm going to attempt to rig something to hook the ...

Other than carefully checking before going ahead to manufacture

Yep, no doubt I'll be doing this a bit more thoroughly from now on.

Interestingly, I found that the WDC datasheets, as far as I can tell, do not specify a single thing about the physical device packages, such as dimensions; they ...

So I randomly decided that I wanted to try my hand at SMD/SMT electronics for the first time ever. I had a design for a simple 65(c)02 SBC, nothing particularly unique there, and I knew the WDC parts came in QFP and PLCC packages, so I just went ahead and converted the design to use the SMT parts ...

Thanks for all the comments so far. I totally agree about the schematic; this was the first one I'd worked on in a while, and the most complex one I'd ever worked on. Since then I've found myself wanting to clean it up and put it on one page, etc. Just haven't done so yet.

The long propagation ...

EDIT: Reading from here: https://wilsonminesco.com/6502primer/addr_decoding.html It says "You must have a way to make sure RAM cannot be written to when phi2 is low!" Does this imply that writes _should_ be qualified by the rising edge of phi2?

EDIT2: I'm not an expert but it seems like qualifying ...

My datasheets say that the 'HC11 is an AND with three inputs, Phi2 among them. The output goes to a 'HC574 that takes its data at the _rising_ edge of its CLK input. But that would be of the leading edge of the signal coming out of the AND.

You should use a NAND instead, that rises its output at ...

Do you have a schematic we could see?
Sure thing. I've attached a PDF. Only difference is that I have already corrected the clock signal thing in the PDF as I did with the bodge wire on the back of the board.
Could you please post a monochrome schematic?

Sure. Just out of curiosity, how come ...

Sure thing. I've attached a PDF. Only difference is that I have already corrected the clock signal thing in the PDF as I did with the bodge wire on the back of the board.

(Fair warning: I'm not an electrical engineer, just a hobbyist; programmer by day)

So, I recently built a rev2 PCB of a 65C02 system I built not too long ago. The changes made were fairly minimal (you could argue I was overly-eager to spin a board, but hey). Mostly just bug fixes, and adding a ...

Glad to hear it's working! Congrats are in order.

If you want to try something more functional, grab the software for my SBC-1... very rich function for a Monitor, BIOS also supports a 6522 VIA for timers and ports.... maintains a RTC and accurate time delays as well... plus a full disassembler ...

Okay, first... there's no need to disable/re-enable interrupts for the CHROUT routine... you also send the character to the ACIA, then execute the delay loop. This ensures that you won't attempt to send another character (by calling CHROUT) until the existing one has completed sending.

If you're ...

Interrupts are enabled for the 6551 Receive, which is working on the W65C51. The transmit interrupt is not enabled by default, you can look at the init code and see how the ACIA is setup. The transmit interrupt is enabled by CHROUT... it takes the character in the A reg, checks for space in the 128 ...

So, the CHROUT routine in Micromon simply puts a character into the transmit buffer, then turns on the transmit interrupt. This won't work on the bad chip. Modify CHROUT so it just send the character to the W65C51, then execute the delay routine to kill enough time for it to be sent. Don't turn on ...

Okay, I have gotten Micromon to boot! However, unsurprisingly, adding a delay loop to CHROUT wasn't enough to get serial output. Does Micromon only try to transmit on the serial port when the transmit interrupt occurs?

For that matter, does the transmit interrupt ever occur when using the WDC 65C51 ...