Serial port permissions -
ignored_mailbox at yahoo.com.au
Wed Oct 19 13:00:15 UTC 2011
On Tue, 2011-10-18 at 10:13 -0700, Brian Mury wrote:
> 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,
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.
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