Apple 1 Clock Section

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Joined: Mar 9 2005
Posts: 79

From the schematic part B1 seems to have pin 1 in an undetermined state when configured for a 6502. The only way I can see the rom being selected is if inputs 1 and 2 on the 00 were high... So...? Do the 74xx series have built in pull-up resistors?

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Joined: Apr 27 2005
Posts: 9
Re: Apple 1 Clock Section

74xx are TTL, you can leave them unconnected... but chips misbehave sometimes, so I usually send to ground all unused pins...

logjam wrote:

From the schematic part B1 seems to have pin 1 in an undetermined state when configured for a 6502. The only way I can see the rom being selected is if inputs 1 and 2 on the 00 were high... So...? Do the 74xx series have built in pull-up resistors?