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Re: [N8VEM-S100:4272] Re: Ithaca Audio Z80 board kit UP & Running with custom monitor!

Grazie mille Fabio ! 
Actually, I wired all addresses of my 2732 to the bus, so I guessed I do not need a pull down... I removed the A10/A11 decoding on the 74138 (U28) as these lines are now connected to the EPROM. The 2732 is fully accessible, to validate that, I set the 2732 at F000 and burned a code from F000 to FFFF finishing with a HALT, and this is how I realized to power on jump to F000 works only 1/2 of the times. I realized the 74138 enables the EPROM sometimes upon reset meaning this probably happens when the address bus is in tri-state so I will probably have to tie down the address lines.
I will work on the docs you kindly sent me and keep you updated.
Ciao, Philippe

Le mercredi 18 juin 2014 23:12:42 UTC+2, Fabio Battaglia a écrit :

Hi Philippe!
I'm traveling right now so can't give you a long, detailed answer.

My board was not 2732 compliant: I had to mod it. Actually, you can fit a 2716... If you use a 2732 remember to pull down the remaining address lines or replicate the monitor code inside the EPROM! Otherwise you'll get erratic behaviour at reset and during work.

I'll send you the schematics and the manual (which includes the EPROM mod instructions) and a revision changelog.
I have yet to ask John King from soundfarm (who kindly sent these docs to me to help) if I can publish them, that's why I'm not pasting them here.


Hi Fabio,
I have the same card but a V1.03 that I got on eBay, worked OK with the original 2708. I noticed though that some mods were done on the board. As I could not read or write the 2708 with my EPROM programmer I decided to replace it by a 2732 and modified the board accordingly. When PROMing a simple program including HALT at the end, I noticed the jump-on-reset to my EPROM is working approx 1/3 times... I think I narrowed this down to the SET input of the 7474 that is used to tri-state the buffers until the Z80 reached the EPROM address. Surprisingly, it triggers while the address bus is still in tri-state, so I was wondering if I need to put some pull-down resistors on the address bus, or check the reset timing..?
Did you make some modifications to have your card work with a 2732 (or is your version already compliant with it ?). Did you experience any issue with the jump-on-reset circuitry ?
If you could send me the schematics of your board that would be great as I am sure some bugs from V1.03 were corrected in your version..
thanks in advance for your feedback !

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