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Old 23 July 2009, 10:54   #6
RedskullDC
Digital Corruption
 
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Join Date: Jan 2007
Location: Dorrigo/Australia
Age: 60
Posts: 355
Hi Kipper2k,

Quote:
Originally Posted by kipper2k View Post
Hi all,

i am trying to create a simple circuit so that when i press a momentary switch with 5V on it it will cause a logic chip to output 5V and remain on once the momentary switch has been released.
...
Any thoughts ?
Turning the machine off/on to select the ROM version would be a nuisance.

Suggest you use a 74LS74 flip-flop.

Tie the CLOCK input to the Amiga's *RESET line.

Wire *SET and *CLEAR both to 5v.

Wire your momentary switch to the 'D' input.

Use either the Q or *Q outputs for your high address bit on the eprom, depending on how you have burnt the kickstart images.

When the machine is turned on, or reset, at the rising edge of the *RESET signal, the 'D' input will be sampled.
The flip-flop will stay in the same state till the next reset

Hope this helps,

Red


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