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Re: [N8VEM-S100:5058] 6502 CPU board questions

John -

Thanks for the hints.

I'm able to input the IOBYTE correctly and echo to the screen.  The monitor recognizes keyboard input and echoes them, just doesn't process correctly.  I think it's a problem accessing RAM, as the symptoms are slightly different with various ram boards - probably upper address line as the I/O ports work fine.

I have another batch of 74LS541's ordered, if that doesn't help I go thru the board wiring again!

- Gary

On Wednesday, August 27, 2014 6:09:47 PM UTC-4, monahanz wrote:

Gary do you have all the jumpers as listed in the yellow table in the “normal” positions.  .  The fact that it can sign means you are almost there.  Sounds like an address line problem or data I/O problem.  After the signon have it input the SMB IOBYTE port and immediately output to console in a loop. Check ASCII character is always correct.

Next do same inputting from Propeller input port.  Next input, place in RAM, read back from RAM and display…





From: n8ve...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of gek...@gmail.com
Sent: Wednesday, August 27, 2014 12:43 PM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:5058] 6502 CPU board questions


I'm trying to get the 6502 Master/Slave CPU board working - and seem to have hit an dead end.

If anyone could confirm what they are using for monitor code, and jumper settings I'd be VERY appreciative!


Minimal system with SMB, 4mb SRAM, Propeller I/O and 6502 most recent Master/Slave PCB.  The SMB, SRAM and Propeller boards work fine with Z80 and 8088 systems.

All testing and assembly worked as expected following John's notes until the 28C64 was installed.

I burned the 28C64 from the 6502mon.bin V1.0 file, with the code starting at 01000H in the 0000H --> 1FFFH space.  01000H thru 010FFH contains 00h as expected, and I can see the jump vector addresses in the top of memory.  0000H thru 0FFFH contain FFH as a fill character.

I had to change the P31 jumper to connect 5-6 to get the monitor to sign on.  Set up as a bus master (only cpu in system).

Now I get the monitor to sign on and print the menu twice.  It then accepts input characters but doesn't respond properly to any.  Single letter commands like "A" just reprint the menu.  Longer commands like D0000,0100 accept the full input and reprint the menu. 

CPU is a W65C02S6TPG-14 purchased thru a reliable source (Mouser) - and I have a second CPU (same source/batch) I've also tried.  I've replaced every other IC except the 74LS541's (I only have a single spare - which I've substituted for every position).  I've resoldered ever connection.  I've tried both 28C64 and 27C64's for the monitor.

- Gary

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