Denial

Hi eslapion,


Thanks for that information. I always wondered and got confused with meanings of the letters that came after the 74 series chips.

Would you be kind enough to let me know the difference between and uses of 74xx and 54xx series chips.


Thanks..

Hi eslapion, Thanks, I'll try your suggestion of 40ns/div. For what it's worth.... I managed to lift a still of the video I just posted. I am sure this is the absolute limit of the oscilloscope. I would say because it's going so hard accuracy may not be reliable. I notice it gets very flakey at the ...

Hi eslapion, Thank you for the clarification on the meaning of. ! & / In regards to !ROMH & !ROML. I have seen it in documents like you described but didn't get the connection. I think in the last photo of my previous post the low voltage on probe A (!ROMH) got to 1.9V. It was a bit tricky T...

Hi eslapion, I managed to observe a simultaneous glitch on pin10 (!ROMH) & pin 11 (!ROML) using the dodgy Winbond PLA substitute PLA on a 250407 'hipric' mainboard. What is the ! for in !ROMH & !ROML? I understand my equipment isn't the greatest and my skills even more so. I notice both trac...

Hi eslapion,


Very interesting....


Yes, these Winbond branded chips are in my opinion non genuine knockoffs from who knows where...

Is it possible to check for simultaneous device activity by observing the outputs on say any 2 outputs of the PLA ? Which are the best candidates to study?

Hi eslapion, Could this be why some think that the Winbond W27C512 EEPROM is a possible substitute PLA? I noted a few forums where there was/is a great deal of discussion about using this Dodgy Winbond EEPROM 27C512 as PLA substitute. Considering that I can observe a glitch on !ROMH & !ROML whil...

Hi eslapion,

Here is were the 2 components are positioned on the board.

Hi eslapion, Many thanks. You drawing my attention to the lower right hand side of this document resolved why I didn't see the capacitor. http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/251138-1of2.gif On my board it's marked as C 203 and is unpopulated. From the document you supplie...

Hi eslapion, I think you're right about the RC filter combination added in the 250407 'hipric' board. I just went through the 3 various 250407 boards I have here. Only the 250407 'hipric' board appears to work correctly with the dodgy Winbond PLA chip. I think I figured out where R42 is positioned. ...

The PLA of the C64 is a 16 inputs, 8 outputs combinational logic device whose function is to generate exceptions in the memory access structure - the CPU can access 64k but the RAM, ROM and IO addresses total more than 64k so where do you want the ROMs and IO to be 'visible' ? The PLA decides that....

Hi eslapion and levoman, I like the gold fingers on your ZaxxDual cartridge levoman. I found this interesting article that GyroGearloose was discussing on another forum.... https://www.computerhistory.org/siliconengine/pal-user-programmable-logic-devices-introduced/ I found it interesting.... Would ...

Hi levoman,

Fantastic you got a site going..well done...

Just a quick question how do we sign in?

I got a reply from PCBWAY on the gold connectors..

Hi levoman,

WOW! That's a great price, good buy....

Have you got any pictures of the glitch on. A dodgy PLA?

Hi eslapion & levoman, No matter if you not an artist in the graphical sense. Looks like a very nice oscilloscope you have there levoman. Much more modern than mine, plus 4 channels no less! https://www.eevblog.com/forum/testgear/hp-54601a-100mhz-oscilloscope-teardown/ What did it cost you all u...

Hi eslapion, Thank you for the information regarding the triggering on the rising and falling edge when looking at the glitch. I am following your method and getting good readings. That doesn't sound like fun with the HASL cartridge connectors. :o I am wondering if one could use something like a gol...