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avatar_orzel

1000$ question about cpc 6128 schematics

Started by orzel, 19:40, 04 August 25

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orzel

Quote from: Bread80 on Yesterday at 22:13If you look at the '464 schematics you'll see that the GA actually has these pull-ups internally on /MREQ, /IORQ, /RD and /WR, as well as on it's open collector output signals - thus saving Sir Alan a few bob in components. I'm not sure why they felt the need for an additional pull-up on the CMOS models. It's probably down to the analogue properties of component pins or, maybe, stricter timing requirements (HC and HCT tend to be a little slower than LS).

I'm not sure to follow. What's the link between /busrq and /iorq ? If /busrq is active, /iorq will go high-z (tristate) and the lack of pull-up will be dangerous in this case ?

I had never looked at the '464. Indeed, a lot of pullups in the ga. That's a difference between 40007/40008 and 40010 ? Or does the 40010 also have those ?

What a complicated way of generating the 16MHz signal... i dont even understand how it works. The same circuit on the 6128 is far more standard (and simpler)

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