Quote:
|
Originally Posted by SVXdc
If a device were to swing from +5 to -5 that would indeed be "legal" for RS-232. But as Phil said, the data output signal emitted by the ECU is standard TTL, 0 or +5 volts. Since it does not swing negative, that won't work for a "true" RS-232 device. Hence using the MAX232 chip (or similar) to convert to -12 and +12V RS-232 levels.
|
The standard does specify negative voltages, but it practice, zero is used. 'True' means nothing here.