MC68000 Pinout 51,52,62,63,64

[zChris]

Hello,

I have added a socket to a Atari 520STfm and done a beeping test to see if the socket has connections. On pin 51,52,62,63,64 im not sure where to probe to see if it has connection.

On reading http://dev-docs.exxosforum.co.uk/520ST_Schematic.pdf it says that for example pin 51 goes to GLUE pin 10. But when i measure there i get no beep.

/zChris

[frank.lukas]

51=A22
52=A23
62=D7
63=D6
64=D5

https://www.nxp.com/docs/en/data-sheet/M68000UM.pdf

[zChris]

Yes but should it beep when i measure between GLUE and mc68000 ?

[PhilC]

Yes but should it beep when i measure between GLUE and mc68000 ?

Yes it should, address and datalines are common across the chips on the ST. Sounds like you might have a broken track?

[frank.lukas]

51=A22
52=A23
62=D7
63=D6
64=D5

https://www.nxp.com/docs/en/data-sheet/M68000UM.pdf

st_glue.png

[zChris]

Yes but should it beep when i measure between GLUE and mc68000 ?

Yes it should, address and datalines are common across the chips on the ST. Sounds like you might have a broken track?

I was in the wrong place probbing. But now when i found where GLUE is (i think i found it anyway) all pins on the socket have connections. Is the beeping test a good test to see if the connections are good enough ?

When i put in DUALTOS + Decoder board i get a white square and a yellow bar around it. With original ROMS and MC68000 in the socket it boots up in TOS.

[PhilC]

@zChris you would probably be better off using the multimeter to measure resistance. One of mine beeps even if you have 100 ohms resistance, which isn't very useful for me.

Maybe also check pin to pin, to make sure you don't have a bridge between two pins and of course you'll need to set those rom jumpers up to use that dual tos board.

[zChris]

@zChris you would probably be better off using the multimeter to measure resistance. One of mine beeps even if you have 100 ohms resistance, which isn't very useful for me.

Maybe also check pin to pin, to make sure you don't have a bridge between two pins and of course you'll need to set those rom jumpers up to use that dual tos board.

Alright ill check with ohm. Yeah i test both positions on the jumper.

[exxos]

Have you simply tried one board at a time to see if you can rule out if it's the ROM board for the decoder board ?

[PhilC]

Have you simply tried one board at a time to see if you can rule out if it's the ROM board for the decoder board ?

That was going to be my next suggestion.

@zChris try it with the original CPU in the socket and the original rom chips, then if that works try the dual tos board with 1.04 and then finally the tos decoder board.