Re: 2/10 serial port B won't transmit

Hello again,

Since I don't know for TTL... :-)

...I tried a different strategy. Unless there's a difference between the Z8530PSH that came on the Lisa and the Z8530PS (no H) that I found for cheap somewhere, the SCC was not the culprit after all.

Back to the original strategy: probing! I'll update if I have any discoveries...

--Tom

On Thu, Oct 26, 2017 at 1:37 AM, James MacPhail <gg__at_email.domain.hidden> wrote:

>
> When no data is transmitted, U9C pin 25 shows 3.66v
>>
>
> For TTL signals, the logic "high" threshold is 2.0V, and "low" is 0.8V.
>
> So, 3.66V is within the specification for a high level TTL signal.
>
> Anything between 0.8 and 2.0V is not high nor low... which is to be
> expected for a signal in transition but may indicate a problem for a steady
> state circuit.
>
> High signals are often much closer to 5V, and low signals much closer to
> 0V; it depends on the parts involved.
>
>
> --
> --
> -----
> You received this message because you are a member of the LisaList group.
> The group FAQ is at http://lowendmac.com/lists/lisa.html
> To post to this group, send email to lisalist_at_email.domain.hidden
> To leave this group, send email to lisalist+unsubscribe_at_email.domain.hidden
> For more options, visit this group at http://groups.google.com/group
> /lisalist
> --- You received this message because you are subscribed to a topic in the
> Google Groups "LisaList" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/to
> pic/lisalist/B_AWH9w7WeQ/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to
> lisalist+unsubscribe_at_googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>

-- 
-- 
-----
You received this message because you are a member of the LisaList group.
The group FAQ is at http://lowendmac.com/lists/lisa.html
To post to this group, send email to lisalist_at_email.domain.hidden
To leave this group, send email to lisalist+unsubscribe_at_email.domain.hidden
For more options, visit this group at http://groups.google.com/group/lisalist
--- 
You received this message because you are subscribed to the Google Groups "LisaList" group.
To unsubscribe from this group and stop receiving emails from it, send an email to lisalist+unsubscribe_at_googlegroups.com.
For more options, visit https://groups.google.com/d/optout.



text/html attachment: alternate version of message