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MSX single step [message #10656]

Thu, 04 April 2024 08:52

jordi.solis
Messages: 119
Registered: March 2017

Senior Member

Hi Guys!
I would like to get your advise.
I'm working to get an MSX cartridge working with the attached schematic, based on the famous Steven Ciarcia's step by step circuit.
It doesn't work and I cannot get to see what's the problem.

Thank you for your support.
Jordi Solís.
MSXmakers!

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Re: MSX single step [message #10658 is a reply to message #10656]

Thu, 04 April 2024 09:45

lynchaj
Messages: 1080
Registered: June 2016

Senior Member

Hi
Does Z80 pin 24 (/WAIT) have a pull up on it? The BAT43 diode is converting U3C into a pseudo open collector output.

Also, are your pull up resistors in RN1 actually tied to VCC? you need to use a bussed SIP resistor network with pin 1 tied to VCC

Good luck! Thanks, Andrew Lynch

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Re: MSX single step [message #10664 is a reply to message #10658]

Fri, 05 April 2024 10:52

jordi.solis
Messages: 119
Registered: March 2017

Senior Member

Hi Andrew,
Thanks for your quick reply!
Yes, all resistors are connected to VCC as shows RN1A.
And yes, as far as I know /WAIT is open collector on the MSX standard and my Omega has a pull up.
I think my problem could come from how the timming is introduced by the 555 and convined by M1 because I have not too munch knoweledge about.
I have added that design to my github at: https://github.com/msx-solis/iBolit/tree/master/iBolit-ngo-kicad

I hope this helps to understand my project.
Regards.

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Re: MSX single step [message #10673 is a reply to message #10664]

Sat, 06 April 2024 15:18

jordi.solis
Messages: 119
Registered: March 2017

Senior Member

News,
I cannot understand how does it work but the /wait signal on the cartridge slot goes to a GAL input
/WAIT = /SLTWAIT
+ /M1WAIT
+ /VDPWAIT
+ /KBDWAIT
KBDWAIT doesn't go anywhere
SLTWAIT comes from both slots (open collector).
VDPWAIT comes from the Video Display procesor
but even worst, M1WAIT comes from a dual flip flop based on the Z80 M1 signal status so... I dont understand how this intecacts with the rest of the circuit.
https://github.com/msx-solis/iBolit/blob/master/readme.md

[Updated on: Sat, 06 April 2024 15:19]

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