About MSX-USB discrete

[denjhang]

Since it is difficult to buy a working CPLD where I live (EPM7064 and the like, usually bought are fakes), I want to build a discrete version of MSX-USB. I want to know about the current discrete version of MSX-USB Is there any error in the schematic diagram? If so, please point it out, and then I will correct it and make the PCB.

[S0urceror]

Hi Liu,

The Kicad files on Github for the discrete version should work. I created a prototype board based on this and it still works after 2 years. You have to make your own PCB. My own development is on the CPLD version which is indeed more difficult to make since you need a programmer and the chips.

Let me know how it goes.

Regards,

Mario

From: Denjhang Liu @.> Date: Tuesday, 3 August 2021 at 00:04 To: S0urceror/MSX-USB @.> Cc: Subscribed @.***> Subject: [S0urceror/MSX-USB] About MSX-USB discrete (#3)

Since it is difficult to buy a working CPLD where I live (EPM7064 and the like, usually bought are fakes), I want to build a discrete version of MSX-USB. I want to know about the current discrete version of MSX-USB Is there any error in the schematic diagram? If so, please point it out, and then I will correct it and make the PCB.

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[denjhang]

The schematic is not connected here, is there a problem?

[S0urceror]

You’re right. Both WR lines should be connected. I corrected it. @.***

Also, if you want it to be RookieDrive compatible and use the appropriate rom file you can switch A4 and A5 on the 74LS688.

@.***

From: Denjhang Liu @.> Date: Tuesday, 3 August 2021 at 15:12 To: S0urceror/MSX-USB @.> Cc: S0urceror @.>, Comment @.> Subject: Re: [S0urceror/MSX-USB] About MSX-USB discrete (#3)

[?????0803211017]https://user-images.githubusercontent.com/61811583/128021260-a60e12c5-300a-40c8-bbf3-bec49d4c3e52.jpeg The schematic is not connected here, is there a problem?

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[denjhang]

Then please take a look at how you said A4 and A5 of 74LS688 should be switched, or which ROM I want to use in which circuit.

[S0urceror]

The 74LS688 is a comparator. It enables the communication to the CH376s chip when the address lines and IO request signal are the same as the pins R0 to R7.

Now it is configured to select the I/O at 0x10 or 0b0001000x. You can change this to 0x20 or 0b001000x. The RookieDrive uses 0x20.

The flashROM has nothing to do with this. It just talks with the Z80 on it’s own set of address and datalines.

From: Denjhang Liu @.> Date: Tuesday, 3 August 2021 at 16:59 To: S0urceror/MSX-USB @.> Cc: S0urceror @.>, Comment @.> Subject: Re: [S0urceror/MSX-USB] About MSX-USB discrete (#3)

Then please take a look at how you said A4 and A5 of 74LS688 should be switched, or which ROM I want to use in which circuit. [?????0803225458]https://user-images.githubusercontent.com/61811583/128038193-5e3fe465-257d-4f9e-a12b-ffacd726ba43.jpeg

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[denjhang]

I understand, then I don't need the compatibility of RookieDrive at present, can the circuit directly use the ROM linked below? https://github.com/S0urceror/MSX-USB/raw/master/drivers/NextorUsbHost/dist/nextor.rom

Thank you for your work and reply.

[S0urceror]

Yes. If you do the RookieDrive compatible setup you use the NextorRD.rom.

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From: Denjhang Liu @.> Sent: Tuesday, August 3, 2021 11:48:35 PM To: S0urceror/MSX-USB @.> Cc: S0urceror @.>; Comment @.> Subject: Re: [S0urceror/MSX-USB] About MSX-USB discrete (#3)

I understand, then I don't need the compatibility of RookieDrive at present, can the circuit directly use the ROM linked below? https://github.com/S0urceror/MSX-USB/raw/master/drivers/NextorUsbHost/dist/nextor.rom

Thank you for your work and reply.

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[S0urceror]

Closing this issue for now. Hope you get the discrete version up and running.