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Re: TF536 + 68000 relocator and ROM board project.
Posted: Mon Sep 28, 2020 10:30 am
by exxos
Use a 22v10 then ? TOS104 why bother to decode it when glue does it, plus TF536 won't run with it anyway..
Re: TF536 + 68000 relocator and ROM board project.
Posted: Mon Sep 28, 2020 10:47 am
by stephen_usher
exxos wrote: ↑Mon Sep 28, 2020 10:30 am
Use a 22v10 then ? TOS104 why bother to decode it when glue does it, plus TF536 won't run with it anyway..
If I'm not using the ROM sockets then I have to do the decoding for TOS 1.x.
I know that the TF536 won't run it but this board will also have a 68000 on it, which you can switch to, and on that you may very well want to run TOS 1.xx. Also, someone may want to use the "TF536" socket/connector for something else other than a TF536 in future.
Re: TF536 + 68000 relocator and ROM board project.
Posted: Mon Sep 28, 2020 1:52 pm
by stephen_usher
OK, this GAL code should do the trick:
Code: Select all
Name TOS 2.06 ROM decoder ;
PartNo 00 ;
Date 28/09/2020 ;
Revision 01 ;
Designer Engineer ;
Company Personal ;
Assembly None ;
Location ;
Device g16v8 ;
/* *************** INPUT PINS *********************/
PIN 1 = A18 ; /* */
PIN 2 = A19 ; /* */
PIN 3 = A20 ; /* */
PIN 4 = A21 ; /* */
PIN 5 = A22 ; /* */
PIN 6 = A23 ; /* */
PIN 7 = !ROM2 ; /* */
PIN 8 = !AS ; /* */
PIN 9 = RW ; /* */
/* *************** OUTPUT PINS *********************/
PIN 13 = !ROE ; /* */
SELECTED=RW & AS & !A18 & !A19 & !A20 & A21 & A22 & A23;
ROE=SELECTED | ROM2;
Re: TF536 + 68000 relocator and ROM board project.
Posted: Mon Sep 28, 2020 8:41 pm
by stephen_usher
I'm getting on with the schematics based upon
@derkom 's CPU relocator Kicad project.
Well, here's my bit anyway (I couldn't make it any smaller and it being legible):
- Schematic-part.jpeg (42.49 KiB) Viewed 3025 times
I just need to add the pin going into pin 20 of the lower ROM (/CE) which is driven by /ROM2.
Derkom, I do have an problem with your Kicad project, it can't find the footprint for the 74HCT157D chips. Also the jumpers aren't documented so I don't precisely know what they do.
So, now I have to try to remember how to define the PCB! I've done it once before, back in April/May but I've forgotten!
Re: TF536 + 68000 relocator and ROM board project.
Posted: Tue Sep 29, 2020 5:51 pm
by stephen_usher
I've a rough PCB layout now.
The dimensions are correct but the placement of the ROM pin is just a ball-park for the moment, but it gives a general idea.
The maximum dimensions are 20cm x 11cm.
- PCB.jpg (83.76 KiB) Viewed 2997 times
I'm going to have to think about holes for screwing support feet as otherwise the board is not going to be stable.
Re: TF536 + 68000 relocator and ROM board project.
Posted: Tue Sep 29, 2020 10:56 pm
by stephen_usher
OK, I've worked out what all derkom's headers were for now... no need to bodge wires now!
Re: TF536 + 68000 relocator and ROM board project.
Posted: Wed Sep 30, 2020 9:52 am
by stephen_usher
Almost there mechanically.
- IMG_2041.jpg (92.46 KiB) Viewed 2950 times
Re: TF536 + 68000 relocator and ROM board project.
Posted: Wed Sep 30, 2020 12:15 pm
by PhilC
Looks good to me @stephen_usher
Re: TF536 + 68000 relocator and ROM board project.
Posted: Wed Sep 30, 2020 6:35 pm
by stephen_usher
PCB order placed with PCBway but I think I've hit the Autumn Lunar Festival so there's probably going to be a 2 week delay, so that'll be 3 weeks in total.
P.S. This is the final board.
- PCB.jpg (183.99 KiB) Viewed 2919 times
P.S. Actually it's only a 5 day delay, so that's OK.
Re: TF536 + 68000 relocator and ROM board project.
Posted: Fri Oct 02, 2020 9:54 am
by derkom
stephen_usher wrote: ↑Mon Sep 28, 2020 8:41 pm
Derkom, I do have an problem with your Kicad project, it can't find the footprint for the 74HCT157D chips. Also the jumpers aren't documented so I don't precisely know what they do.
Sorry for late reply. It's been a really busy week.
I got the footprints from SnapEDA, who have footprints for almost everything. The specific page for these muxes is
here.
The jumpers aren't jumpers, except the one labelled SW. SW is the switch for selecting which CPU is active. All the other pin headers on there are for sending the switched signals over to CPU1, because I didn't want that socket switched on the PCB, as I wanted to be able to plug in devices that required those signals regardless of switch state. So, the left hand 64-pin socket doesn't have anything switched, and the 68000 that I have stuck on the top of my stack has the switched pins bent out and connected to these jumpers.
This post explains it, and
this one shows photographs of what I mean.
If you're designing a board that is just a switcher, and doesn't need to provide these signals to one socket regardless of switch position, then you should just switch these lines the same way on both sockets.
Edit:
stephen_usher wrote: ↑Tue Sep 29, 2020 10:56 pm
OK, I've worked out what all derkom's headers were for now... no need to bodge wires now!
Oh.
