Re: Noob question: examine arbitrary memory address? #ELF #memory


Lee Hart
 

P Todd Decker via groups.io wrote:
Should all the LS chips be replaced with HC? And, if so, can the originally specified 47K resistor values be maintained?

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P. Todd Decker
913-284-8814

On Sep 26, 2020, at 1:24 PM, Lee Hart <leeahart@earthlink.net> wrote:

´╗┐ca1naj610 wrote:
Thanks, Lee for the suggestion to substitute a 74C10 for a 74LS10.
Since many of us have 74HC chips, what would be the consequence of
substituting a 74HC10 for the 74LS10?
Sure; a 74HC10 would work as well as the 74C10. I was just thinking of a vintage chip that would have been Elf-period correct, without having to rewire it for a 4023.
I haven't looked at the RC1802 schematic closely. But the diode OR gates in the original PE Elf used 47k pull-down resistors. Since they all drove CMOS inputs, it worked.

The problem comes because the N2/LOAD signal can't drive a 74LS input (much less 3 of them, as would happen if the PE Elf's IC10 was a 74LS10 instead of a 4023).

That makes me wonder: How does the RC1802 drive the TIL311 hex displays? The PE Elf used eight 4050 buffers to drive its display, because these are TTL parts. They would overload the bus without the buffers.

Lee

--
A designer knows he has achieved perfection not when there is
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--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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