Re: high level on different 6502

From: didier derny <>
Date: Sat, 5 Nov 2016 21:56:00 +0100
Message-ID: <>

the 65c02 high level was near VCC

I had 2 Synertek 6502 both were at 2.5v for the high level...

2 differents machines   SYM1 and  CBM8032, same results...

      looks like the problem is linked to the synertek

On 05/11/2016 21:50, Francesco Messineo wrote:
> On Sat, Nov 5, 2016 at 9:37 PM, didier derny <> wrote:
>> while checking some signals on the 6502 of my 8032 motherboard
>> I found the 'high' level rather low 2.5v  (I expected around 4v...)
>> so I took my SYM1 board and tested several 6502
>> MOS         6502       around  4v
>> Rockwell  6502       around  4v
>> Rockwell  65c02     around  5v
>> Synertek  6502       around  2.5v
>>                   CM630   around  4v      (bulgarian clone)
>> I tried several 6502 of each type...
> 2.5V is really a bit outside the acceptable output High level for TTL logic.
> 2.7V is the official minimum level for the High state. However, TTL
> inputs should accept as High any voltage => 2V.
> If the current capability of the outputs isn't degraded (i.e. if 2.5V
> is maintained at all the inputs when loaded at the max fan-out), I'd
> say it should still work.
> CMOS outputs, on the other hand, should go to the power rails, if they
> aren't broken.
> Do you have many Synertek and they all have the same output levels?
> Frank
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Received on 2016-11-05 21:00:45

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