• Please review our updated Terms and Rules here

Cbm 2001 Pet strange boot

It is, you just need to learn a new trick!

I would use the external X trigger with a separate probe monitoring BA15 and triggered on a HIGH to LOW transition.

The four address inputs to the 4:16 decoder (SN74154) continuously count up in binary from 0000 to 1111 and then wrap around to 0000 and keep repeating. BA15 is the most significant bit of this counter. A transition on BA15 from HIGH to LOW signifies the start of this 0000 to 1111 counting sequence.

You have to select the time base to trigger from the external probe rather than channel 1 of the oscilloscope.

You can then use channel 1 of the oscilloscope to probe on the 'select' outputs of the '154 - but (this time) they should be perfectly stable and we can see what is going on!

Remember, the oscilloscope is a tool - not a magic oracle!

Dave
 
Why so desperate?!

Your oscilloscope is a powerful tool. However, you have still only used 10% of its capabilities...

Dave
 
I would use the external X trigger with a separate probe monitoring BA15 and triggered on a HIGH to LOW transition.
A simpler approach is to simply use CH2. Put the CH2 probe on BA15. Adjust the timebase to one cycle of BA15 fits. Move the Trigger to CH2 and use the -ve edge mode, then adjust the trigger level until everything stops moving.

IMHO Two channels is enough for all this.

All the probing for the decode circuitry is so much more obvious, whilst NOPing, when it is compared to a single cycle of (B)A15
 
A simpler approach is to simply use CH2. Put the CH2 probe on BA15. Adjust the timebase to one cycle of BA15 fits. Move the Trigger to CH2 and use the -ve edge mode, then adjust the trigger level until everything stops moving.

IMHO Two channels is enough for all this.

All the probing for the decode circuitry is so much more obvious, whilst NOPing, when it is compared to a single cycle of (B)A15
Sorry but i don't understand :(((((
Why need i use CH2? It's different from Ch1??
Thanks so much!!!
 
Ba15 on cpu ord ud2??
It doesn't matter.

Nivag is suggesting using channel 2 for the trigger (monitoring BA15) and then we use channel 1 to probe with.

Channel 2 is our trigger (reference in time), and (assuming we adjust it correctly) will cause the oscilloscope trace (on channel 1) to be static whilst we look at it.

Dave
 
Can i take Ba15 from this connector?
 

Attachments

  • Schermata 2022-06-26 alle 20.24.46.png
    Schermata 2022-06-26 alle 20.24.46.png
    25.7 KB · Views: 3
This is best setting to see BA15 on ch2 :(

Set the TRIGGER to CH2 (slide switch on right)
Set -ve edge
Adjust trigger level.


trigger.PNG

I am only guessing from the picture as I don't have a manual for this device... I'm not sure what "TRIG ALT" does! try on and off!... Also not sure about "AUTO" versus "NORM"!

Just fiddle around with the knobs until you get a stable trace.
 
Last edited:
Ok, can be good now?
Zoom out slightly (i.e. change timebase) so you see a full cycle (and a bit), then move it down to the bottom half of the display and then get working on adding CH1 (and move the CH1 trace into the top half). We are aiming for two traces... one in the top half and one in the bottom.

PS
I am unavailable for a few days now... hope to see some progress on my return!
 
Last edited:
Lots of knobs to twiddle...

channels.PNG

DC coupled should work... these signals have a common ground. Select DUAL... use position to put CH1 in top half of screen... use position to put CH2 in bottom half... use Volts/Div to make them fit in their sections of the screen

Looking forward to seeing some beautiful traces
 
Ok now i have CH2 (connected with BA15) in botton half screen and CH1 in the middle....correct?
 
Back
Top