exxos's Atari, Amiga & retro forum

Next steps:

• Burning TOS ROM

• Put all the chips in

• Attach a SM124

• Open the window to release potential smoke

• Power-up

But this is something for next Sunday…

Thanks for the photos...almost makes up for not having any retro time for the past few weeks....

:thumbup: :thanksblue:

Ok, swapped two items of my task list ;)

Looking like a proper Alpha board now
:bravo: :2k2:
Not going with a "bad DMA" then ;)

exxos wrote: 20 Mar 2024 20:42 Looking like a proper Alpha board now
:bravo: :2k2:
Not going with a "bad DMA" then ;)

„Bad DMA“ - right :D
Will be added to my list of changes

Hi,

Just a short status (didn’t have much time due to „normal life“):

• Board doesn’t start, so need to do some more measuring

• Screen is black but there is a sync - at least the Monitor „reacts“

• Checked RAM - I screwed up PinOut of the 4MB RAM Board from the original ATX, but PinOut at SIMM looks fine

Not sure if I will find time during Easter, but I have two questions:

• I burned two TOS (1.04/2.06) into the 27C4096 the following way: TOS images padded to 256k, byteswapped, concatenated - right?

• what is the purpose of the two H5 jumpers for Blank-select and Blank-enable? Do I need them at all? If not, what is the default position?

Hi,

Time for an update…

Due to real life problems, it took some time…

I have populated my 2nd revision of the H5 STX
Most of the errors identified in the 1st revision were removed and looking good.
But, unfortunately the board is not booting.
In color mode I have a solid white screen, in Mono (jumper set) the screen remains black. But the monitor gets sync, i.e. the screen is not a real black (like being off) but a very dark grey.
From the signals at the 68k socket I see, that halt is always low...

I have a known good chipset and known good RAM

So I did some tests according this thread: Troubleshooting H4 and H5


Power:
Input (bench supply) 5.15V
Board in idle mode: 4.92V
Consumption (in idle mode): 900mA (PLCC 68HC000), 1.15A (DIP 68k)

Reset:
Working as expected, going high after 1-2s

Pull-ups:
As expected
Had a flaky MMU, where A19 measured only 1k. Without MMU 2.2k. With new MMU now also 2.2k

Shorts/Solder Joints:
Measured no shorts on the busses
Visual inspection (several times) showed no shorts or bad solder joints
…you can never be 100% sure, I know

1st power up:
Under Reset the signals at the 68k socket are as expected

Clocks:
Scoped all the required clock signals - all as required and looking good

1st clock cycle:
As described I removed the CPU and grounded the required signals at the 68k socket and measured the data bus.
All data bus signals which supposed to be high, are high (4.9V) but the ones which should be low are at approx. 2V

So, something blocks the data signals from going low.

While checking the schematics and layout around MMU and data bus isolation/buffering (244/373) I realized the mistake.
I mixed up pins 1 (OE) and 11 (LE) at the 373...
I do not know how often I double- and triple checked the schematics, and didn’t recognize it.
Might explain that it does not boot - but most probably the black screen in Mono mode has a different root cause… let’s see.

So, time for some bodge wires…

Will do this at the weekend.

Cheers
Michael

My H5 STX is alive :mrgreen:

Color & Mono
TOS 1.04 & 2.06
Floppy also working
Time for some more detailed tests… step by step…

Setup looks a bit crazy… :D

:yay:

Congratulations. Looks good!