ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

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shadow338
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ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by shadow338 » Tue May 09, 2017 5:51 pm

Hello,

Can I use the following schematic (attachment) that was taken from the 128K ZX Spectrum Harlequin and adapt on the 48K version?Or do I need to pay attention to anything in special?

Thanks!
Attachments
AY-3-8912.jpg
AY-3-8912.jpg (81.57 KiB) Viewed 551 times

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1024MAK
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by 1024MAK » Thu May 11, 2017 6:32 pm

shadow338 wrote:
Tue May 09, 2017 5:51 pm
Hello,

Can I use the following schematic (attachment) that was taken from the 128K ZX Spectrum Harlequin and adapt on the 48K version?Or do I need to pay attention to anything in special?

Thanks!
You need some decoding circuitry to drive the control inputs (CLK, BC1, BDIR) to the AY-8912 chip.

Mark

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kokkiklhs
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by kokkiklhs » Wed May 24, 2017 7:29 pm

You need some decoding circuitry to drive the control inputs (CLK, BC1, BDIR) to the AY-8912 chip.
Mark
Which means...???
Please, could you explain with a little more detail?
Has anybody done it, fitting a real AY inside a plain 48k speccy?
A step-by-step photo tutorial for dummies would be great from someone that has already done it, I mean a lot of people would like to do that and (in theory) it shoudn't be that difficult...
I don't like the external AY boards, but having searched a lot during the past years, I didn't find a good guide for that purpose around the web...

P.S. Should I open a new topic? Am I hijacking here?
:roll:

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1024MAK
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by 1024MAK » Wed May 24, 2017 7:57 pm

I think it has been done for a ZX Spectrum+ where there is more room. Someone has even upgraded one to 128k RAM.

There is this project

I'm not aware of any step by step instructions.

In order for the CPU to send data to the AY sound chip, some logic circuitry has to detect the address output by the CPU, and that the the CPU is trying to access a input/output device. This requires some extra logic chips. Either standard 74LSxxx or 74HCTxxx logic chips, or a programmable logic chip.

If you want the AY sound chip to have the same address as in 128k Spectrums, then you have to use the same address detection (called address decoding).

There are some details in the link I have included above. Note that I have not had time to check to see what addresses this design uses.

I'm sure you will have more questions... ask away.

As fitting to a Sinclair Spectrum or a Harlequin is similar, I don't think there is a need to open a new thread. Unless of course shadow338 would prefer this.

Mark

superfo
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by superfo » Sun Jun 04, 2017 7:23 am

see attached file, note: Y1 is not used.
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SCHEMATIC1 _ PAGE1.pdf
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shadow338
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by shadow338 » Sat Jun 10, 2017 8:16 pm

thanks superfo!

I was looking at the pdf provide and I have a few questions:

1 - is that Ok if we don't include the Kempson part of the circuit? (U5 + U6)

2 - How we hook up the AUDIO out of the AY to the harlequin original speaker or/and original EAR?


thanks!

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1024MAK
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Re: ZX Spectrum Harlequin kit (48K). How to add AY-3-8912 ?

Post by 1024MAK » Sat Jun 10, 2017 10:33 pm

@shadow338 Yes, if you do not want the Kempston joystick port, leave out U5, U6, D1, D2 and J2.
shadow338 wrote:
Sat Jun 10, 2017 8:16 pm
How we hook up the AUDIO out of the AY to the harlequin original speaker or/and original EAR?
In an ideal world, you would use some resistors to form a simple mixer that feeds into an amplifier. One set of resistors and one amplifier for mono, two sets if you want "stereo". However, that is not what you are asking for...
I will have to have a look a the Harlequin schematic first...

Unless Superfo beats me to it :mrgreen:

Mark

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