exxos's Atari, Amiga & retro forum

Forgottenmyname wrote: 20 Sep 2018 18:34 My PSU needed a quick tweak, was running at 4.93 between 7 and 14 of the LS11 which was the same value on the floppy power connector

Thats good then...

I would check resistance of the whole address and databus (power off of course) Each resistor pack pin to 5V and make sure you have 2.2K on each one..

The address bus resistor packs 4,6,8..

Databus packs 2,3.

Also check
/AS on GLUE (pin 34)..
UDS (pin 47)
LDS (pin 46)
R/W (pin 55)

Also check those pins with power on (voltage scope) see what they are doing..

Just checking now. First thing i notice is some of my resistor packs are 4.7K, no 2.2K ones.

I don't suppose that makes a difference?

will check the datalines etc next

4.7k is fine.

exxos wrote: 20 Sep 2018 18:34
Also check
/AS on GLUE (pin 34)..
UDS (pin 47)
LDS (pin 46)
R/W (pin 55)

Also check those pins with power on (voltage scope) see what they are doing..

Ok, all the resistances seem ok to 5v, checked the cpu to mmu address lines ok.
checked glue to cpu data lines ok
/AS is 1mhz square wave,
/AS on Glue is 2mhz square wave
UDS,LDS and R/W all high.

Forgottenmyname wrote: 20 Sep 2018 20:52 Ok, all the resistances seem ok to 5v, checked the cpu to mmu address lines ok.
checked glue to cpu data lines ok
/AS is 1mhz square wave,
/AS on Glue is 2mhz square wave
UDS,LDS and R/W all high.

What is the address and databus doing on the scope ?

Address bus should all be low to read the first byte in ROM... You may have to keep pressing reset or setup a trigger on your scope as even ROM OE might pulse low once after reset without you seeing it ?

Ok, will have a look tomorrow, she who must be obeyed is calling.

Hi - How are you getting along?

Would like to see if your board is in the same state mine is - if you are seeing bombs with that weird shifting pattern or something else.

Icky

Not yet icky but hope to have some more progress later tonight.

I'm just wondering if the main difference has been that I'm using the mum ram instead of the falcon ram?

Can you post a image on how you have fitted the ram board ?

exxos wrote: 21 Sep 2018 18:49 Can you post a image on how you have fitted the ram board ?

Here we go.