Serial port permissions -

Tim ignored_mailbox at yahoo.com.au
Wed Oct 19 13:30:53 UTC 2011


Brian Mury:
>> You should see +12 volts or -12 volts (actually anything between 3
>> and 15 meets the spec, but you'll usually see somewhere around 12).
>> Negative voltages are high, positive voltages are low,

Tim:
> Other way around...  A high (digital 1) is a positive voltage, a low
> (digital 0) is a lower or negative voltage (i.e. less than the 1's
> voltage, whether it be zero or below zero).
>  
> All digital logic is this way.  There are cases where the low signal
> is the active state (i.e. a 0 is true and 1 is false), called
> "negative logic," or "active low," but it's still a case of 1's
> voltage is greater than 0's.  It's the meaning of 0 and 1 that's
> inverted.

Scratch that...  Serial *data* lines are backwards.

Gawd I hate negative logic.

-- 
[tim at localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

Don't send private replies to my address, the mailbox is ignored.  I
read messages from the public lists.





More information about the users mailing list