danw
Lifetime Supporting Member
Why are the data bits inverted (from the way the bits appear on the scope)
1) Bernie said so in his post above.
2) I remember something to that effect from having messed with RS-232 on a scope some years ago.
3) The initial data word was revealed, and the only way to get it to 'fit' is to 'invert' what one intuitively thinks is the logic state.
4) an interpretation of the EIA standard at the link I posted above states, "a logic high will appear as a low voltage between -3v and -15v when probed on the bus". Something about the drivers inverting the logic. Remember the little circles on the tips of triangles reperesenting the drivers in digital logic circuits? Probably what's inside those serial chips.
Dan
1) Bernie said so in his post above.
2) I remember something to that effect from having messed with RS-232 on a scope some years ago.
3) The initial data word was revealed, and the only way to get it to 'fit' is to 'invert' what one intuitively thinks is the logic state.
4) an interpretation of the EIA standard at the link I posted above states, "a logic high will appear as a low voltage between -3v and -15v when probed on the bus". Something about the drivers inverting the logic. Remember the little circles on the tips of triangles reperesenting the drivers in digital logic circuits? Probably what's inside those serial chips.
Dan
