high level on different 6502

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high level on different 6502

Didier Derny
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...




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Re: high level on different 6502

Francesco Messineo
On Sat, Nov 5, 2016 at 9:37 PM, didier derny <[hidden email]> 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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Re: high level on different 6502

Didier Derny
Hi

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 <[hidden email]> 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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Re: high level on different 6502

Francesco Messineo
On Sat, Nov 5, 2016 at 9:56 PM, didier derny <[hidden email]> wrote:
> Hi
>
> 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

the High voltage at 2.5V isn't  a problem in itself (if it keeps the
level when loaded). TTL logic real "bad" noise margin is on the low
level (0.5V max output vs 0.8V max input).
So in theory 2.5V High should work as it has a still better noise
margin than the correct Low levels. Look also at the actual Low level
voltages on these parts however.
Then, one might wonder if Synertek parts were always marginal or they
didn't age well, but I can't surely tell :)

>
>
>
> On 05/11/2016 21:50, Francesco Messineo wrote:
>>
>> On Sat, Nov 5, 2016 at 9:37 PM, didier derny <[hidden email]> 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
>>
>>         Message was sent through the cbm-hackers mailing list
>
>
>
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Re: high level on different 6502

Didier Derny
In fact it's my question :)  aging synertek 6502  or strange 6502 from
synertek

for the low level I've not noticed anything special

they all looked slightly above 0, the same for all 6502 tested


I'm connecting the 6502 bus to a 3.3v chip with 1k resistors... (a
propeller)
not sure if the signal would still be ok after the 5v to 3.3v conversion
if the high level is at 2.5v
the goal of the propeller is to catch the write between $8000 and $8fff
and produce a video signal on vga

I'm retrying the tests of my board after having replaced the synertek  
6502 by a mos 6502



On 05/11/2016 22:01, Francesco Messineo wrote:

> On Sat, Nov 5, 2016 at 9:56 PM, didier derny <[hidden email]> wrote:
>> Hi
>>
>> 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
> the High voltage at 2.5V isn't  a problem in itself (if it keeps the
> level when loaded). TTL logic real "bad" noise margin is on the low
> level (0.5V max output vs 0.8V max input).
> So in theory 2.5V High should work as it has a still better noise
> margin than the correct Low levels. Look also at the actual Low level
> voltages on these parts however.
> Then, one might wonder if Synertek parts were always marginal or they
> didn't age well, but I can't surely tell :)
>
>>
>>
>> On 05/11/2016 21:50, Francesco Messineo wrote:
>>> On Sat, Nov 5, 2016 at 9:37 PM, didier derny <[hidden email]> 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
>>>
>>>          Message was sent through the cbm-hackers mailing list
>>
>>
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Re: high level on different 6502

Segher Boessenkool
In reply to this post by Francesco Messineo
On Sat, Nov 05, 2016 at 10:01:31PM +0100, Francesco Messineo wrote:
> the High voltage at 2.5V isn't  a problem in itself (if it keeps the
> level when loaded). TTL logic real "bad" noise margin is on the low
> level (0.5V max output vs 0.8V max input).
> So in theory 2.5V High should work as it has a still better noise
> margin than the correct Low levels. Look also at the actual Low level
> voltages on these parts however.

The 6502 datasheet says output high is at least 2.4V.  The RIOT (6532)
datasheet says input high is at least 2.4V.  If the outputs can only
reach 2.5V then they will be slow ramping up to 2.4V, as well.

> Then, one might wonder if Synertek parts were always marginal or they
> didn't age well, but I can't surely tell :)

Did you measure it with any (external) load?


Segher

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Re: high level on different 6502

Didier Derny
the measure was taken with an oscilloscope directly on the 6502,

for the loads they are the one normally on the bus

I've not added anything on the bus


On 06/11/2016 00:04, Segher Boessenkool wrote:

> On Sat, Nov 05, 2016 at 10:01:31PM +0100, Francesco Messineo wrote:
>> the High voltage at 2.5V isn't  a problem in itself (if it keeps the
>> level when loaded). TTL logic real "bad" noise margin is on the low
>> level (0.5V max output vs 0.8V max input).
>> So in theory 2.5V High should work as it has a still better noise
>> margin than the correct Low levels. Look also at the actual Low level
>> voltages on these parts however.
> The 6502 datasheet says output high is at least 2.4V.  The RIOT (6532)
> datasheet says input high is at least 2.4V.  If the outputs can only
> reach 2.5V then they will be slow ramping up to 2.4V, as well.
>
>> Then, one might wonder if Synertek parts were always marginal or they
>> didn't age well, but I can't surely tell :)
> Did you measure it with any (external) load?
>
>
> Segher
>
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Re: high level on different 6502

Gerrit Heitsch
In reply to this post by Didier Derny
On 11/05/2016 09:37 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...

Since I was curious and able to test it... A few years ago I built
myself a replica of the EMUF232 on a perfboard (was a real pain in
the...). That's a 6502 system with 2 x 6522, 1 6551, 32KB RAM running at
1.8432 MHz. As a CPU I used a SY6502A, datecode 8047.

When checking the address lines on the scope today, the CPU produces a
HIGH of 3.5-3.7V. So it can't be Synertek in general unless the drivers
are less powerful than Rockwell and MOS and your board has more load on
the lines. If possible, check the SY6502 in another board, maybe a 1541.

  Gerrit









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Re: high level on different 6502

Didier Derny
I only have 4 boards with a 6502

cbm 8032

SYM 1

MICRO KIM

REPLICA 1


same result on cbm and sym, I'll try on the micro kim and replica 1

note: the replica 1 has an instability and crash often  (seems due to
the propeller)

I'll try on these 2 boards



On 06/11/2016 15:13, Gerrit Heitsch wrote:

> On 11/05/2016 09:37 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...
>
> Since I was curious and able to test it... A few years ago I built
> myself a replica of the EMUF232 on a perfboard (was a real pain in
> the...). That's a 6502 system with 2 x 6522, 1 6551, 32KB RAM running
> at 1.8432 MHz. As a CPU I used a SY6502A, datecode 8047.
>
> When checking the address lines on the scope today, the CPU produces a
> HIGH of 3.5-3.7V. So it can't be Synertek in general unless the
> drivers are less powerful than Rockwell and MOS and your board has
> more load on the lines. If possible, check the SY6502 in another
> board, maybe a 1541.
>
>  Gerrit
>
>
>
>
>
>
>
>
>
>       Message was sent through the cbm-hackers mailing list


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Re: high level on different 6502

Didier Derny
In reply to this post by Gerrit Heitsch
tried on the MICRO KIM 1 and 2 REPLICA 1  4v with rockwell 6502 2.8 / 3v
with synertek
it is clear that there are less components on the bus of these 2 machines

changing the 6502 with a higher high level does not change the
instability of the replica 1  tenth edition...
these machine are rebuild made by Vince Briel, the micro kim and the
replica 1 TE are working fine
the replica 1 tenth edition is a nightmare... a finger around the
propeller reset the 6502 every 2s (about)
never found a solution... I thought that changing the 'high' level could
solve the problem...
on the replica 1 te   the 5v->3.3v is done with 74ls245 + 1k resistors
on the replica 1 tenth  the 5v -> 3.3v is done with 1k resistors
directly on the bus

this second replica is about to be reduced to a stack of component + pcb
for the trash :(


On 06/11/2016 15:13, Gerrit Heitsch wrote:

> On 11/05/2016 09:37 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...
>
> Since I was curious and able to test it... A few years ago I built
> myself a replica of the EMUF232 on a perfboard (was a real pain in
> the...). That's a 6502 system with 2 x 6522, 1 6551, 32KB RAM running
> at 1.8432 MHz. As a CPU I used a SY6502A, datecode 8047.
>
> When checking the address lines on the scope today, the CPU produces a
> HIGH of 3.5-3.7V. So it can't be Synertek in general unless the
> drivers are less powerful than Rockwell and MOS and your board has
> more load on the lines. If possible, check the SY6502 in another
> board, maybe a 1541.
>
>  Gerrit
>
>
>
>
>
>
>
>
>
>       Message was sent through the cbm-hackers mailing list


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