Re: Logic levels question 6502A (Missile command)

David Shoemaker wrote:
>
> I am trying to trouble shoot a board. I am getting some odd responses
> reading the roms. I noticed that the address lines coming from the
> 6502 seem to be going high at 3.5 -- 3.7 vdc. I suspect this is
> causing some of the ttl to not latch high.
>
>
>
> This is checked through a meter using the fluke to read a particular
> address on a loop and using my scope for the same and while running
> the game.
>
>
>
> Is this a normal value? I don't see any pull-ups on the address lines
> on the schematic.
>
>
>
> David
>
Don't forget the Fluke pod has it's own address and data line buffering.
There are notes about watching out for that in the pod manuals...

Input Low Voltage ..... 0.8V max.
Input High Voltage...... 2.0V min., +5.0V max.
Output High Voltage ... 2.4Vmin. with loh = -250ua

etc. (Page 1-4, 6502 Instruction manual)

(and Logic High is a minimum of 2.4 as per Rodger)

John :-#)#

-- 
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
                 www.flippers.com 
"Old pinballers never die, they just flip out"
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