Is the designer of that ELF available? Is there any ECO or Error fixes listed? I wish I had time to build the same project, but I've got too many projects piled on my bench and more on the shelf.
I don't think it's abnormal for MRD cycles. I believe in Load Mode, the 1802 is just executing IDLE instructions (00) but without advancing the PC.
From: firstname.lastname@example.org <email@example.com> on behalf of John Kennedy <johntkennedy@...>
Sent: Monday, September 21, 2020 4:27 PM
To: firstname.lastname@example.org <email@example.com>
Subject: Re: [cosmacelf] Noob question: examine arbitrary memory address? #ELF #Memory
[Edited Message Follows]I wish I had another kit to check the CPU signals :-) I might have to get the Membership Card after all! At the moment I’m suspicious that when I set up the system to load a byte into memory and press IN, the MRD signal pulses - but keeps pulsing from then on. Shouldn’t it stop once the byte is in memory? MRD triggers the STROBE signal, so the display keeps updating rather than latching after an OUT.
Update: Ah - interesting. The version of the Elf I built looks like it’s missing a pull-up resistor to reset the flip-flop that would eventually switch off MRD. This might explain a few things. Some more investigation required.