I've built an RC6502 SBC Apple 1 replica, and I'm having an issue right off the bat. I asked about this on the RC6502 group on Facebook, and we weren't able to come up with a solution. So I thought I'd ask the Apple 1 gurus here.
After some initial serial issues, I have it up and running at what seems like a working monitor prompt. But when I try to run the machine code test program in the Operations Manual, I get no output. I can type in a Hello World loop BASIC program and it works fine, but I can't get machine code to run from the monitor. Any ideas? I'd like to get this working, then see if I can make an ACI board that will work with it.
How are you entering BASIC? When you boot it up, and get the monitor prompt, are you typing E000R to get the actual basic prompt? If so, wozmon is working enough to set the memory location to where BASIC is and start executing it.
Yes, BASIC seems to be working fine. At least well enough to execute a very simple print loop. That is exactly how I am launching it.
Ok, well that is good!
I presume you are using a serial terminal to interact with the machine? If so, are you sending the machine code over that or typing it manually? When sending text to Apple1/clone over serial, you need to specify a character and line delay, else the computer will miss some of the characters.
Also I assume you're referring to the test program that echoes all the characters repeatedly, but if not, please share the program :)
Yes, that is the test program I am using, and I'm typing it in manually. Before I try pasting in a large program, I figure I should get the simplest one running first.
Ok, good deal. I haven't completed an RC6502 (Backlogged, if I ever get to it. I have 3 Replica 1+ units, a Ben Eater inspired DB6502, and a completed 'real' Apple 1 replica) so I can't try to reproduce this, unfortunately. I could try to run the code on a R1+ maybe.
After you enter the test program, can you echo it back by entering the memory range? After entering the code, instead of entering the 'R' to run it, enter 0000.001f and press return (Arbitrary end value). See if the program you entered was sucessfully stored in memory.
Yep. All that checks out. Here is a typical session:
\
0
0000: FE
0:A9 0 AA 20 EF FF E8 8A 4C 2 0
0000: FE
0.A
0000: A9 00 AA 20 EF FF E8 8A
0008: 4C 02 00
R
I found the solution. I had been using a WD65C02, as the project said it was compatible with the SBC version of the RC6502, but not with the multiboard version. I was suspicious, so I swapped in the R65C02 from my Apple IIe, which required a jumper change on the board. Still didn't work. Still suspicious, I bought some origninal MOS 6502s, and now it's working. Apparently, the RC6502 has problems with 65C02s of any sort. Thanks for the help.
Great troubleshooting and glad you sorted it! Congrats on the build.