Aloha! First time troubleshooting a 6502 SBC. I built a RC6502 from a kit I bought online. I have a TL866II Plus, I've used it to test the 138, 04 and 00 ICs. I also made sure the 28C256 contents match what is in the BIN file I pulled down from github. And, I've tested the 6502 in an Apple II Plus. The Aruduino Nano is also working, and it displays "RC6502 Apple 1 Replica" when powered on.
From that point, the TX LED on the Nano is stuck, as the LED stays green. Same thing on the term program end, where the RX is constantly on, and it receives CRs. Resetting both the Nano and the SBC doesn't change anything.
With a logic probe, A12 thru A15 are stuck on HI. I do get pulses on PH0, 1 and 2. RST is HI. It appears to be based on these findings that the CPU is somehow stuck. The photos show the jumper settings. I believe the ROM and RAM are enabled, and A13 and A14 jumpers are set to the 8K window at $0000-$1FFF.
Can anyone pick up on where I may have misconfigured something?
RC6502 SBC - First time troubleshooter
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floobydust
- Posts: 1394
- Joined: 05 Mar 2013
Re: RC6502 SBC - First time troubleshooter
You've not given us much info... but I managed to locate what appears to be the project:
https://hvetebolle.blogspot.com/2017/08 ... a-sbc.html
Your PCB is a later level than that shown in the link, but hopefully you can verify that the schematic is in fact correct.
Basic troubleshooting:
1- Measure all the chips to make sure they are getting +5 volts and that the grounds for each is also at ground.
2- Make sure the Reset signal is working, i.e., it goes for low for a period of time, then goes high.
3- With power off, make sure none of the address lines are shorted to each other, ditto for the data lines.
4- Check to see of the IRQ or NMI is going low, checl BE to ensure it's at +5V as well.
5- Ensure you have a running 1MHz clock signal.
6- Make sure ALL of the pins are straight and properly inserted into the socket... you might have one that curled under.
7- If all else fails, you'' likely end up metering the PCB to ensure all of the signals are correctly routed and have continuity without any shorts.
Then again, it's always possible that you have a bad chip on the board or the Arduino isn't correctly setup.
https://hvetebolle.blogspot.com/2017/08 ... a-sbc.html
Your PCB is a later level than that shown in the link, but hopefully you can verify that the schematic is in fact correct.
Basic troubleshooting:
1- Measure all the chips to make sure they are getting +5 volts and that the grounds for each is also at ground.
2- Make sure the Reset signal is working, i.e., it goes for low for a period of time, then goes high.
3- With power off, make sure none of the address lines are shorted to each other, ditto for the data lines.
4- Check to see of the IRQ or NMI is going low, checl BE to ensure it's at +5V as well.
5- Ensure you have a running 1MHz clock signal.
6- Make sure ALL of the pins are straight and properly inserted into the socket... you might have one that curled under.
7- If all else fails, you'' likely end up metering the PCB to ensure all of the signals are correctly routed and have continuity without any shorts.
Then again, it's always possible that you have a bad chip on the board or the Arduino isn't correctly setup.
Regards, KM
https://github.com/floobydust
https://github.com/floobydust
Re: RC6502 SBC - First time troubleshooter
floobydust wrote:
1- Measure all the chips to make sure they are getting +5 volts and that the grounds for each is also at ground.
2- Make sure the Reset signal is working, i.e., it goes for low for a period of time, then goes high.
3- With power off, make sure none of the address lines are shorted to each other, ditto for the data lines.
4- Check to see of the IRQ or NMI is going low, checl BE to ensure it's at +5V as well.
5- Ensure you have a running 1MHz clock signal.
6- Make sure ALL of the pins are straight and properly inserted into the socket... you might have one that curled under.
7- If all else fails, you'' likely end up metering the PCB to ensure all of the signals are correctly routed and have continuity without any shorts.
2- Make sure the Reset signal is working, i.e., it goes for low for a period of time, then goes high.
3- With power off, make sure none of the address lines are shorted to each other, ditto for the data lines.
4- Check to see of the IRQ or NMI is going low, checl BE to ensure it's at +5V as well.
5- Ensure you have a running 1MHz clock signal.
6- Make sure ALL of the pins are straight and properly inserted into the socket... you might have one that curled under.
7- If all else fails, you'' likely end up metering the PCB to ensure all of the signals are correctly routed and have continuity without any shorts.